♪♪ -This is St.

Mary's Church, Cholsey, Oxfordshire.

It is the hiding place of an extraordinary secret.

The secret of success.

Our mission is to find it.

Buried here, in a quiet, unassuming corner of this hallowed ground, is a writer who, within her lifetime, achieved almost unimaginable fame.

She has sold a staggering 2.3 billion books.

Second only to Shakespeare, she is the most widely published author of all time.

Her name is Agatha Mary Clarissa Mallowan, better known to us as Agatha Christie.

♪♪ The secret of Agatha's success is hidden, of course, not in the grave at all, but in her writing.

It's a secret that stares us in the face every time we open one of her books.

We just can't see it.

So the search begins.

A unique research unit has been gathered from several universities around England.

Dr.

Richard Forsyth, research fellow in applied linguistics at the University of Warwick.

Dr.

Pernilla Danielsson, academic champion of communications technology at the University of Birmingham, and Dr.

Marcus Dahl, research fellow at the School of Advanced Study, London University.

They will use a specially designed system of linked high-speed computer programs.

One of these programs is known as Concordance, a 21st century version of an ancient code-breaking science.

♪♪ It was a science that began in the Middle Ages, when theological scholars started to look at the Bible in a novel way.

They were hoping to achieve a greater understanding of the mysteries believed to be hidden in its passages by looking for patterns, messages, codes, mortal techniques to help them read the Word of God.

To do this, they had to create a way of studying groups of words to reveal secrets invisible to the naked eye.

♪♪ This invention was to become one of the most powerful computer systems in the world.

It was used by Richard Forsyth in two extraordinary investigations.

First, during the 1996 elections, when New Labour was on the brink of victory.

A sharply critical-yet-anonymous newspaper article appeared threatening to dash Tony Blair's first chance of government.

The author was mysteriously called Cassandra, but who was hiding behind the name?

Dr.

Forsyth raced against the clock.

The evidence he uncovered put Ken Livingstone squarely in the frame, although he has yet to admit it.

And, most famously, this amazing computer technology exposed the anonymous author of "Primary Colors."

During the 1992 U.S.

elections, someone wrote an extremely embarrassing account of Bill Clinton's presidential campaign.

The story caused a scandal across the United States.

-Mandy, did you write this book?

-No.

Wish I did.

It's a great book.

-You did not write this book?

-No, I didn't.

-Come on, Paul, say it.

You're back in Austin -- -Not me, Larry.

No.

Word of honor.

I didn't do it.

-I must say, I admire the publisher and the author.

It's the only secret I've seen kept in Washington in three years.

-Once again, the author, a Newsweek journalist, Joe Klein, was unmasked by the power of this extraordinary computer technology.

The same technology that is now reaching into the core of Agatha's writing, into the very heart of this most private of people.

-She was born, I think, in Devon, or in the West Country somewhere, or lived in the West Country somewhere.

And she lived and wrote, I suppose, her most famous works between the wars.

That's about all I know.

-I only ever knew her as the gray-haired lady of the photograph they used in all of the plays.

Whenever there was a play, they always put that photograph of her in the program.

-I don't believe we do know who she was and I don't believe we ever will.

There's nothing that I've read that paints a picture for me of who this woman was, this woman with this amazing knowledge of crime.

-She actively shunned publicity.

And she is somebody who sought to keep themselves very, very private.

-Agatha is a mystery to all of us.

I think she has many hidden facets, and I don't think we'll ever know the full story behind Agatha, because she was very careful, I think, to cover her tracks, just as a good murderer would.

-I don't know who she was.

-Agatha was born into a creative family, most of whom wrote in one form or another.

However, by the time she was a little over 5 years old, Agatha's mother, Clara, suddenly decided no child should be taught to read before the age of 8.

But the remarkably gifted young Agatha had other ideas.

She loved to listen to the stories her governess would read her, until one day, she found she was able to read her favorite book, "The Angel of Love."

-"What lovely presents we have!"

-Agatha's governess was forced to admit, apologetically, that Miss Agatha could read.

[ Both laugh ] Agatha's father, Frederick, whom she adored, decreed that if she could now read, she should learn to write.

This she didn't enjoy nearly as much, finding it difficult to distinguish individual letters.

Having learned to read by the look of words, her spelling was always of the hit-and-miss variety.

For years, Agatha neither attended school nor had any official teachers at home.

It seemed certain that, from an early age, Agatha was already a special girl.

She already showed signs of a remarkably individual intelligence.

♪♪ Her first published work was at the age of 11, when the local paper, campaigning against the introduction of trams to Ealing, included her poem.

"When the electric trams did run.

In all their scarlet glory.

'Twas well, but ere the day is done.

It was another story."

Because she didn't go to school and meet friends, she had to rely on herself for entertainment and created an imaginary-but-solitary life at home in Torquay.

Mundane day-to-day existence was always rich in possibility.

And if the paper boy didn't turn up, Agatha's agile mind would construct a murderous plot.

-Six, five, four... -Sometimes, when her elder sister Madge came back from school... -You don't really think... -...she would play disturbing mind games with Agatha.

♪♪ A precocious mind can turn in on itself and cause undue torment.

-There is a sad part, though, to the day.

-The fairy-tale life of a big, rambling house, with its dark recesses, could also become a source of anxiety.

Over and over, she suffered a recurring nightmare in which her family was threatened by a shadowy figure, a gunman dressed in military uniform.

Imagination and reality became blurred.

In an instant... [ Gunshot ] ...a happy family gathering could become an awful nightmare.

♪♪ [ Gun cocks ] ♪♪ [ Gunshot ] Agatha's childhood continued to have a haunting undercurrent.

After her father's death, the 13-year-old was overcome by fears that her mother, too, might die.

Suffering the helpless panic that only a child can, She took to sitting just outside her mother's bedroom door at night, listening intently for the sound of her breathing.

Coming up, we discover how this sensitive little girl created a unique formula, a recipe for success that would captivate millions of fans.

Dr.

Marcus Dahl is given special permission for an historic viewing of Agatha Christie's secret notebooks.

And we take a journey into the dark world of divorce, disappearance, and trance.

Agatha Christie is the most successful author of the 20th century.

Our special research team is using the latest computer technology to find the key to her phenomenal success.

Already, Dr.

Pernilla Danielsson is proving there is something very special about Agatha's writing.

-I'm looking here at my results from a comparison between Agatha Christie's books and Arthur Conan Doyle's books.

And I'm trying to find clues to what makes her text special and different from his text.

And here's a word -- "answered" In his books, people answered questions.

Why don't they do that in Agatha Christie's?

I mean, she doesn't have to use that word.

She can use words like "replies," "responded," "spoke," "repeated," "explained," anything like that.

But does she?

If we go in and search for it here, almost exclusively, she uses the word "said."

"Said" is a much more general verb than "replied" and "responded," but she uses this all the time.

We already know that she's not trying to be Shakespeare.

She doesn't try to introduce new words, new phrases.

Middle-range English.

That's fine with her.

She uses this sort of everyday language and she repeats it.

So she's not challenging you with her vocabulary.

You are free to focus on the plot.

-Agatha may never have written a detective story at all if her sister Madge hadn't bet against her.

-Agatha's sister Madge was ostensibly the better writer.

She'd been published in Vanity Fair and she later had a play on in the West End.

She was a very gifted woman in her own right and a more dominant personality than Agatha.

According to Agatha's autobiography, they had a chat one day, sort of, "Could you write a detective story?"

And they both sort of said, "Oh, I don't know."

"Could you?"

"Could you?"

You know, and Madge, her sister, sort of said, "Well, I bet you couldn't," you know, as sisters do.

-...to guess who the murderer was.

-Agatha sort of agreed that she couldn't do it, but then she said the germ of the idea was in there.

-It wasn't until the First World War, whilst working as a nurse, that Agatha finally took up the challenge and wrote her first book, "The Mysterious Affair at Styles."

It was written in quiet moments amidst the chaos of wartime England.

The plot relying heavily on her newfound knowledge of poisons.

She had recently qualified as a dispensing chemist, and that knowledge would serve her well throughout her writing career.

The book wouldn't find a publisher until 1920, more than five years later.

It would be a moderate success and well-reviewed, especially by The Pharmaceutical Journal.

The remarkable thing is, at her first attempt, Agatha established a template that would last throughout her career.

She got it absolutely right from the word "go."

Dr.

Danielsson is looking at a graph in which each dot represents an individual book, and each book has been analyzed for word length, word frequency, and sentence structure.

-Each red dot is one of Agatha Christie's books.

And all the green dots is one of Arthur Conan Doyle's books.

And all the blue ones are from the British books in general.

What's amazing with this is, even though I move this screen around, you will see that all of Agatha Christie's books, they end up very closely linked together.

They've clustered in one spot.

That means that her books are very similar in style.

They use the same number of letters in a word, same number -- oh, on average, of course -- same number of words in a sentence, on average.

And that's consistent throughout her career.

So it doesn't change much from the beginning till the end.

And if you look at that, compared to, for example, Arthur Conan Doyle's work here, he is spread out.

There's something that is unique for her texts that are the same in all of her texts, almost as if there was a formula here.

-The computer indicates the most typical Agatha Christie mystery is "Evil Under the Sun."

Its formula clearly illustrates the way she captivates her readers.

British crime writer Val McDermid has been a fan since childhood.

-There are a few core elements that make up almost any Christie you can think of.

For a start, there is a body very early on, sometimes before the book opens, but there is a body.

There is a closed group of suspects.

There are only a certain limited number of people who can do this.

It may be closed physically because they're on an island or on a ship or on a train or something.

Or they may be closed socially because they're the only people who had access to the particular milieu of the murder.

And then you have the detective, who can either be one of her series characters -- Poirot, Miss Marple -- or it may be someone that we're meeting for the first time, who is caught up in this crime in one way or another.

You have a series of red herrings and dust thrown in the reader's eye to make us think that we're getting somewhere, we know what's going on, we think we've got it.

-I wish you to consider very carefully a bathing cap, a bath, a bottle, a wristwatch, the diamond, the noonday gun, the breadth of the sea and the height of the cliff.

From that, you should be able to solve it yourselves.

-And then, finally, you have the denouement, where the detective gets everyone together and he goes through the red herrings and the clues and explains to us benighted readers why it is that only one person could have committed this crime.

And here's the reason why, and here's the reason why all these other people are eliminated.

-I came to the conclusion that it was you... Madame Redfern.

-Me?!

-And then you have solution, closure at the end.

-My God!

You're a wonder, Poirot.

♪♪ -I remember reading a description of when the first Poirot books came out -- because they were her first books -- of people actually reading them like this.

They couldn't put them down.

It wasn't because there was bloodthirsty or sex in there.

There was the mind.

It was like a Sudoku.

How?

How?

How?

How?

How?

And then they never get it right.

-Ex-commander Roy Ramm of New Scotland Yard believes Agatha's work can be of great benefit in actual crime fighting.

-I think one of the key elements that I really love about Agatha Christie's books is that she actually can teach the power of observation very keenly.

One of the stories that I read recently was, you know, a man falls in a wood, stumbles.

Someone rushes towards him, helps him up, turns, there's blood on his hands, but there is no murder weapon.

And all of a sudden, people are leaping off and thinking, "Well, this is supernatural."

Well, the reality is that Agatha quickly says, "Well, actually, the man stumbled on a root.

The man that went to his assistance took the opportunity to stab him and withdrew the knife."

If you think about it, it was the only thing that could have happened, and it was there right from the start.

But she hid it cleverly by disguising it in the supernatural and the attitude of the other characters all the way through.

-Our team of investigators is leaving no stone unturned in its attempt to reveal the Agatha Christie Code.

Every aspect of her fascinating story is another piece of the jigsaw puzzle.

Suddenly, our investigators are given a wonderful opportunity.

Dr.

Marcus Dahl is invited by Agatha Christie's only grandchild to see Agatha's notebooks.

These are the books she used to plan her novels.

They have never been seen by the public.

This truly is a first.

But what will they reveal?

-One of the things I found most interesting when we're looking at the notebooks of Agatha Christie was the imprecision of it.

It's not something you necessarily would think of when you think of Agatha Christie, the great crime-fiction writer, the organized mind.

You see shopping lists on the back of her notebooks, games, puzzles that she was obviously playing, perhaps with her husband, Max.

You could see their initials, their names.

You had a real sense of the artist at work, but in a way that you wouldn't necessarily expect in a detective writer.

You might expect it in a poet.

One of the things that was great interest was the pace of which Agatha Christie seemed to be writing.

There was this one section we saw where she had written 14 pages or so.

It looked literally like she then stuck a line through each section very quickly.

And then the next section was this perfectly written out section without crossings-out, without mistakes, occasional line.

At some point, her mind had clicked and she'd reached this zone sportsmen might talk about or this groove, if you're a musician, a deeper level of consciousness.

She's reached it and she's got it down, and then it's all there.

And perhaps that's when something is happening to the reader where, because Agatha Christie's flow is so defined and so precise, perhaps, once it's resolved itself, then she's sucking the reader into this unconscious sort of trance.

-Agatha was able to write anywhere, anytime.

Writing seemed to come easily to her.

Success in her personal life, however, would prove much harder to find.

-Agatha was a very attractive girl.

She had a lot of suitors.

And she was engaged to this chap, Reggie Lucy, who was a self-effacing man, who said, "I'm going to go away.

And if I come back and you still feel the same, we'll get married."

He went away, and she met Archie Christie, who was a dasher.

They got married in the first winter of the war, Christmas Eve 1914.

And I think the pressure of war and the heightened excitement of the time probably infected their relationship, to an extent.

-Five years into their marriage, Agatha's only daughter, Rosalind, was born.

This was to be a complex, troubled, yet deeply affectionate relationship.

Agatha described her as a bright, beautiful, terrifying child.

She wrote, "There is nothing more thrilling in this world, I think, than having a child that is yours and, yet, is mysteriously a stranger."

From an outsider's point of view, things couldn't have been better.

-She says that it was almost the most contented time of her marriage, and at the same time, there must have been something not going right, because although, on the surface, everything was happier than it had ever been, within a couple of years, Archie had told her he'd fallen in love with another woman and wanted to leave her.

Which I think came as a shock that I don't think she ever quite got over.

-Then it all began to unravel at the seams.

On Friday, December 3, 1926, Agatha Christie vanished from her home in Berkshire.

Her car was later found abandoned in Surrey with her clothes and papers inside, but no sign of the famous author.

She vanished for 10 days in all and could not remember a moment of it.

-The sense of solitude for her at that time of her life must have been quite overwhelming.

It wasn't just that she'd lost her husband or was about to lose her husband.

Her mother had died.

Her mother, to whom she was incredibly close, to whom she could have talked the whole thing through.

And all she really had was this child, who doted on Archie and actually said, "He wants to be with me.

It's you he doesn't seem to like."

And she had to keep up appearances to Rosalind.

So she had no one really to whom she could sort of break down.

So what could she do?

She went away to break down.

Doesn't seem to me to be that mysterious.

-Agatha spent the time at the Harrogate Hydro, having signed in using a name similar to that of her husband's mistress.

The incident doesn't appear in her autobiography, and she never mentioned it again.

Next, our research team throws some light on Agatha's darkest hour and takes us beyond her plotlines to reveal the unexpected effect Agatha's writing has on our minds.

-I believe the main reason Agatha Christie is so successful is because of the pattern of addiction that she creates in her readers through brain chemistry.

-Could this explain why "The Mousetrap" became the longest-running play of all time?

-People like it, but who can say why?

-Following the breakdown of her marriage, Agatha Christie disappeared.

The incident lasted 10 days, and afterwards, she could not remember a moment of it.

However, Dr.

Danielsson and Dr.

Dahl believe two of her books tell a different story.

Just before and just after her disappearance, Agatha wrote "The Murder of Roger Ackroyd" and "The Mystery of the Blue Train."

It seems that both books contain certain words that reveal her disturbed psychological state at the time.

-She's coming up with these strange words, which seem oddly like they're an unconscious memory of her altered state of mind.

-Mm-hmm.

-These words -- "affected," "lunatic," "asylum," "anxiety," "curious," "madness," "identity," "haunted," "vague," "premonition."

And then this marvelous passage where it sounds like she's summing up with what the doctors have said to her about perhaps her illusionary condition or something.

"The doctor immediately snorted with contempt, 'Brain fever, brain fever?

No such thing as brain fever.

An invention of novelists.'"

-But don't you think this was a way for her to deal with what had happened?

Because she never wrote about the disappearance in a way, not in her autobiography or anywhere else.

And like you were talking about before, that this creative state she was in, this flow, this trance-like state, perhaps her disappearance was just that she got into a much deeper version of that, and afterwards, she couldn't remember anything.

-Darian Leader is one of Britain's most celebrated psychologists.

He has his own opinion about Agatha's memory loss.

-It's sometimes said that in those two weeks, Agatha Christie was suffering from an amnesia, but it seems that there's very little evidence that it was amnesia.

She didn't approach anyone to try and find out something about her identity, as amnesiacs often do.

She didn't approach a policeman or someone in uniform, something that happens commonly in amnesia, the kind of behavior you might expect from an amnesiac patient.

On the contrary, it seems much more probable that she was in a trance-like state.

[ Match strikes, flame whooshes ] ♪♪ -In the early 1900s, séances were extremely fashionable, and falling into a trance was all the rage.

Agatha's mother, Clara, was known to have experimented.

However, although they appear in at least 10 of her stories, Agatha herself never attended a séance.

Her logical mind distrusted anything supernatural.

And apart from that, the role of the medium often attracted money-seeking fakes and confidence tricksters, who hoodwinked vulnerable clients using cheap theatrical tricks and amateur dramatics.

♪♪ -It's fascinating, how Agatha treated spiritualism or whatever, because some of her early stories in particular are... You know, use it heavily.

And that may have been because her mother had written sort of ghost stories and that kind of thing, and she was obviously -- adored her mother.

Because later on, in -- I can think of at least two of her books -- the plot resolves itself upon the fact that spiritualism is a load of old tat.

For example, a séance that everyone believes in, and, actually, it's somebody setting up an alibi for themselves or something like that.

So -- But at the same time, she is this odd mix of pragmatism, understanding love of the ordinary, grasp of the ordinary, all the things we can relate to, and, yet, this other, definitely more mystical side.

-So although the occult appears in her writing, it's unlikely to explain her success.

For that, we must turn to the computer analysis of the words she wrote.

In addition to 80 crime novels, Agatha penned at least 50 plays, including one very special one.

♪♪ ♪♪ "The Mousetrap" was a present for Her Majesty Queen Mary's 80th birthday.

It quickly broke all British box-office records and, in 1962, celebrated an unprecedented 10-year run.

-People like it, but who can say why?

-How many years would you give "The Mousetrap" yet?

-I wouldn't like to prophesy.

I've always said, "It's coming off next year" for years, but it never has, so... -And it looks very much like it never will.

It's now in its 53rd year and still going strong.

But there's a new show in town.

"And Then There Were None" is a classic Agatha Christie murder mystery with a twist.

Classic because it's set in a confined space -- in a hotel on a small island -- plenty of red herrings, and anyone could have done it.

[ Jazz music playing ] The twist is, there is no detective to solve this seemingly impossible puzzle.

♪♪ Ten people unknown to each other are invited to a house party.

-Would you care to dance, Miss Claythorne?

I'd be delighted, Mr.

Marston.

-The host doesn't show, but his evil intentions quickly become clear.

-Ladies and gentlemen.

-Who said that?

-May I have your attention?

-It's the record!

Look!

-Your attention, please.

-What the devil?

-I accuse you, Edward George Armstrong, on March 14, 1925, of causing the death of Louisa Mary Clees.

-What?!

-Shh!

-I say!

-Rogers, take it off.

-No, no, no.

Leave it.

-I accuse you, Vera Elizabeth Claythorne, on August 11, 1935, of killing Cyril Hamilton.

-Outrageous!

Quite outrageous!

-Emily... -If we were able to look 53 years into the future, would we be looking at another "Mousetrap"?

Has Agatha done it again?

Is there a formula that we buy into time after time?

-Her critics often accuse Christie of writing the same book 80 times.

In fact, I think they couldn't be further from the truth.

It's hard to look at Christie now, given all that we know subsequently, all that we've read subsequently, but, actually, her books were remarkably innovative.

She twisted the basic plot of the detective novel, the basic formula, if you like, the basic conventions into all sorts of shapes.

I don't want to give anything away to people who haven't read the books, but "The Murder of Roger Ackroyd," "The Murder on the Orient Express" -- these are things that had never been done before and, you know, have been imitated since.

She took this basic idea that you have a crime and a detective and a solution and lots of confusion along the way and gave it lots of different shapes.

No one in Christie is safe from suspicion.

It can be the character that you're most liking that you suddenly discover is the killer.

Sometimes, though, it's not the character you like most.

Sometimes, it's the character who has very good reason for you to dislike them.

People often say about Christie, "Oh, it's always the least likely person."

Well, it's not always the least likely person.

Sometimes, it's the most likely person, after you've gone all around the houses of the least likely people.

But at the end of the day, what she does is make every story, I think, different.

-Television hypnotist Paul McKenna sees Agatha's work in a different light.

-Agatha Christie is a formulaic writer.

Even though all the stories are different, the template is always the same.

And human beings like that.

We like the consistent and the familiar.

In research studies, when people are asked about what they most fear, "the unknown" always rates very highly.

That's why, say, with an Agatha Christie story, there is a bit of uncertainty at the beginning, in that we don't know who committed the crime, but you always know by the end who did it, and that we can rely on.

That's part of the appeal.

James Bond is pretty much the same story each time.

The characters change a bit, but it's always the baddie who wants to take over the world, who, you know, Bond defeats in the end.

And so when people criticize Agatha Christie by saying, "Oh, but all the stories are the same," that's the genius of it.

-So Agatha's appeal seems to be her ability to write non-formulaic formulas, a difficult and confusing concept for us to grasp.

But somehow, Agatha managed it time and time again.

After the divorce from Archie, Agatha made the transition to full-time writer.

Not only was it a financial necessity, it was a way of moving forward with her life.

♪♪ She threw herself into writing and traveling and fell in love with the Middle East.

♪♪ On a trip to Baghdad to take part in an excavation, she met Max Mallowan, a brilliant and, to her, a very exciting young archaeologist.

Agatha's family was very suspicious of his motives, and she was reluctant to accept his offers of marriage.

But then she softened.

Max asked her whether she would mind spending her future with someone whose profession was digging up the dead.

She wrote back saying, "I adore corpses and stiffs."

♪♪ Their marriage was a success.

They had found perfect companions in each other.

She delighted in helping him on his archaeological digs, cleaning and cataloging artifacts, becoming quite an authority on the subject herself.

Life with Max in the cradle of civilization was a profound source of inspiration for her.

Many of her famous mysteries, including "Death on the Nile" and "Murder on the Orient Express," were influenced by her regular visits to the Middle East.

She found she could write anywhere and was extraordinarily prolific.

80 books, 50 plays, and at least 120 short stories.

The words just seemed to flow, and these words have an appeal that has never been equaled.

Will her secret ever be revealed?

♪♪ Dr.

Marcus Dahl believes he has found a key that could unlock the mystery.

-What we're finding in Agatha's work is a level of repetition of key concepts, in almost like a cloud of words, where the words occur in a condensed space and relate to each other heavily across very small spaces.

So, for example, here, she's thinking about life.

And the word "life" and words that are analogous to life occur rapidly.

"Life."

"Life."

"Death."

"Life."

"Life."

Then there's ideas of instinct to live.

"One doesn't live."

"Reason assents to living."

"Would be better dead."

"Who would die."

And this is just one little paragraph.

This is literally within a very small period of time.

Now, we don't know exactly what this means yet, but it's something to do with how her concepts of vocabulary are related to the key themes that she's developing in her books.

-Neuro-linguistic programming is how language affects the mind.

-David Shephard is an expert in the new science of language -- neuro-linguistic programming.

He's spent a lifetime studying the way words can have an effect on the way we think and feel.

-The research showed that Agatha actually repeats words at least three times in a particular paragraph.

In NLP, that's something that we call a meta-program, and it's particularly one of the meta-programs that enables us to become convinced about something.

So, in this particular paragraph here, we have the words "remembrance," "remember," "remember."

That fills our convincer so that we're absolutely convinced, in that paragraph, that it's about remembering things.

That means that Agatha is, moment by moment, controlling the mind of the reader.

They know what that paragraph's about.

It's about remembering.

And they can now move on to the next paragraph, knowing full well that they know what the previous paragraph was about.

-One of the interesting things we're finding here is how Agatha introduces quite complex ideas with a rapidity that you might expect would put off readers looking at her works.

For example, in "Then There Were None," 10 characters introduced in great rapidity with these contradictory character traits, which is a complex thing to take on board as a reader.

And, in fact, perhaps that's one of the things that makes it challenging at first, and, yet, actually oddly compelling.

-A person's conscious mind has very limited focus.

It can only concentrate on somewhere between five and nine things at any particular point in time.

Once we go over nine things, the conscious mind can't track that, and literally, the person goes into a hypnotic trance.

The way that Agatha Christie uses this in her books is, she writes novels with more than nine characters, with more than nine plotlines taking place at any particular point in time.

The reader's conscious mind can't track that.

It becomes overloaded, and the reader literally goes into a trance.

Now you're experiencing the book.

Now you're feeling the book, not just thinking about it.

You lose yourself.

This is when you think you've read for 10 minutes, you look at your watch, and discover you've been reading for an hour.

You're on your way home, reading the book on the train, the bus, the tube, and you miss your stop.

Also, because feelings are infinitely more memorable than thoughts, what people do is, they associate the feelings with Agatha Christie's name and also with her novels.

The next Agatha Christie book comes out, people want the feeling again.

They have to go buy the book.

They have to read it and they have to finish it.

-Suddenly, it looked like the investigation was on the right track, and the next revelation would reach far beyond anyone's expectations.

-It's just another example of what makes her an exquisite hypnotist.

-Agatha Christie's phenomenal success seems to be rooted in our unconscious experience of her books.

[ Screaming ] -I think one of the reasons we love any detective fiction is that it's safe to be scared in there.

[ Screaming continues ] And we love to be scared safely.

Adrenaline is a fantastic drug.

It's legal, it's free, and we can turn it on almost at will.

It's the fight-or-flight thing.

[ Screaming continues ] It's the same way that we go on a roller coaster and scream our heads off because we're absolutely terrified, and then we come off and we join the queue to go on it again because it was so fantastic to be that scared.

But it's scared in a safe place.

We can read this.

We can be excited.

We can be terrified.

We can be made uneasy.

We can feel the mist creeping in off the marshes.

We can feel the eeriness of the dark ancestral hall closing in around us and those footsteps coming out of the darkness.

[ Thunder crashes ] But we know it's safe.

The detective will save us from what's bad and horrible out there.

[ Thunder crashes, rumbles ] -As you read Agatha Christie's books, you see that everyone in a village or small town or community, in fact, turns out to have had a motive for the murder.

♪♪ ♪♪ And then you take games like Cluedo, where you're trying to work out who the murderer is.

And the great paradox of those games is the fact that you're playing them with your family, with a close community, with your friends.

And isn't the lesson that we learn from Agatha Christie the fact that, really, we've probably got murderous wishes towards all the people that we're playing the Cluedo game with?

♪♪ ♪♪ ♪♪ ♪♪ -Of course, the one major difference with Cluedo and reading a Christie is that you don't have the responsibility when you're reading the book to figure it out.

You can rest yourself in the hands of Miss Marple or Poirot.

But with Cluedo, you actually have to go out there on the high wire and be Miss Marple or Poirot.

You have to take the risks.

You have to make the decisions.

You eliminate suspects.

You eliminate possible weapons.

You eliminate locations.

You have to make the choice at the end.

-Where would human beings be if they didn't have the belief that somewhere, someone knew something, knew about the mysteries of human life, knew about the things in life that we can't explain or make any sense of?

And one of the captivating things about Agatha Christie's books is that she creates little worlds in which, at the end, everything is explained.

There's someone there -- Poirot or Miss Marple -- who reveals things to us, who explains things, who solves the mysteries.

In other words, it's a universe in which meaning prevails.

-Dr.

Dahl has discovered an ingenious device in Agatha's writing.

It seems to confirm Val McDermid's adrenaline theory.

-We're very excited at what we're finding about how Agatha is controlling the speed at which we read her books.

The way she does this is by changing the level of descriptive passages.

There are more descriptive passages at the beginning of her book than there are at the end.

This has the effect of streamlining her plots so that we read more quickly towards the end of her books.

Literally, we're rushing towards the end.

-So Agatha appears to be writing in a way that not only grips the reader's attention, but very precisely controls the act of reading itself.

-I believe the main reason Agatha Christie is so successful is because of the pattern of addiction that she creates in her readers through brain chemistry.

When we crave something, we release a chemical called dopamine.

It's the motivation neurotransmitter.

When we satisfy ourselves by getting what it is that we want, we release serotonin, which is the happy neurotransmitter.

It makes us feel high.

So what she does is introduces us to these characters who may well have committed the crime and leads us down an alley.

You know, one at a time, she begins to make us think that this might be the one who did it.

And we crave to know the answer because we want to resolve it in our minds.

And then she kills that character off or she leads us in another direction.

So the craving just builds and builds and builds.

And after she's done that several times, we're dying to know, which is why people feel that they have to read the book faster and faster -- to get that resolution.

And then, at the end, finally, we find out who did it, we flood our brains with serotonin, and we feel fantastic.

And that's the addiction, which means we have to go and then read another one to have it all over again.

-All the data is in.

We've discovered that Agatha Christie is unique among writers.

Particular linguistic patterns set her apart.

The computer has found repeatable, predictable processes which control the way we read her stories.

She uses linguistic techniques which initiate trance-like states.

And her writing is like cocaine.

Once we've tried her books, we are involuntarily driven, like drug addicts, compelled to read her books again and again.

But there was to be one more revelation.

The father of neuro-linguistic programming and a man widely recognized as a global authority on hypnotherapy, Dr.

Richard Bandler, believes Agatha Christie is actually hypnotizing her readers.

-A great hypnotist has to be able to sound very specific, but yet remain artfully vague so that they can capture the attention and allow people to fill in their own details.

By leaving things vague, what happens is that it doesn't disrupt the flow of attention.

If you want to lead people's attention from here to there to here to there so that it goes in a specific direction, as soon as you start putting in too many details, people start having to erase pictures or they have the wrong picture or the wrong color or the wrong facial expression.

If you say it's a dilapidated square, people get to paint their own picture, and you don't disrupt the chain of thought.

It allows them to stay in the trance that you want them in so that they're headed in the right direction.

And if anything is the Agatha Christie Code, I think that's what it is.

♪♪ -Is it true?

Has Agatha Christie actually hypnotized us?

Does her writing actually induce a hypnotic trance and stimulate our brains in the same way that class-"A" drugs can?

Could this be the stunning truth behind Agatha Christie's amazing success story?

At the end of our journey, extensive computer analysis seems to confirm such a hypothesis.

This is truly a bewildering and astonishing breakthrough.

A quantum leap forward in our understanding of how a long-dead writer can still hold us under her spell.

This is the genius of Agatha Christie.

This is the Agatha Christie Code.

♪♪ ♪♪ ♪♪ ♪♪