It was one of the most notorious disappearances of the 20th century and has perplexed biographers ever since.
But BBC historian Lucy Worsley now believes she has gotten to the bottom of Agatha Christie's 1926 disappearance arguing that it was prompted by a rare psychological state caused by emotional trauma.
Worsley has said that Christie entered a “fugue state”, in which sufferers lose their sense of self while experiencing amnesia and setting off on journeys to unexpected locations.
Worsley, who has researched the episode for a biography titled Agatha Christie, told BBC History magazine: "This mysterious disappearance of 11 days seems to be the central injustice of Agatha Christie's life.
She added: "By 1926 Agatha was a successful novelist, and she was under a lot of pressure to keep producing books. But her mother died that year, and she went into an episode of what today would be described as a depression.
"She reported forgetfulness, tearfulness, insomnia, an inability to cope with normal life. Her mental state became so bad that she considered suicide. She then entered, I believe, into a fugue state.
"Now, this is a very rare condition, and it causes you to step right outside your normal self and adopt another persona, so that you don't have to think about the trauma you've been experiencing in your current situation."
In the winter of 1926 the 36-year-old Christie had experienced the loss of her mother, and had just discovered that her husband Colonel Archibald Christie was having an affair. Worsley believes these events could have been sufficiently traumatic to trigger a fugue state.
In December 1926 the novelist’s car was found abandoned near Guildford, and after police began a manhunt rumours began to circulate that Christie had taken her own life. Newspaper articles at the time suggested that her own house, rumoured to be haunted, may have triggered the strange disappearance.
The search for Christie may have involved up to 15,000 volunteers, and the media attention led some to speculate that the vanishing was a publicity stunt, a claim angrily denied by the author’s secretary who said she was “too much of a lady for that”.
Detectives consulted Christie's own work in a bid to understand her motives, but the author eventually turned up in the Yorkshire town of Harrogate, with no memory of what she did or who she was. She had booked into a hotel under the name Mrs Tressa Neele, and “Neele” was years later proven to be the surname of her husband's mistress.
Stunt to spite husband
This dramatic event, and the reference to her love rival, has led some subsequent theorists to speculate that Christie intended the whole event – which she barely spoke of again – as a stunt to spite her cheating husband or frame him, but Worsley disagrees.
She said: "That's not framing your cheating husband for murder, that is living with a really serious mental health condition.
"And yet the narrative is that she was somehow a bad person who was playing some sort of trick on the world; to frame her husband or get attention to sell novels."
A few months after Christie’s ordeal she filed for divorce from her husband. Two year later, the author remarried and her ex-husband married Ms Neele.
Christie gave one interview touching on the subject of her disappearance, in which she alluded to wanting to deliberately crash her car, but deciding against it. She later bumped her head while driving and said that after this moment she was no longer “Mrs Christie''. She did not mention the incident in her autobiography.