Despite her success, Christie always insisted for a modest life and tried to keep a tight rein on the family finances. It is said that her attitude in this regard created tensions in her conjugal relationship with Archie and soon he entered into an affair with his 25 year old secretary Nancy Neale. Finally, on the evening of 3 December 1926, after a tough fight, Archie sought for a divorce from his wife and left their home to spend a weekend away with friends, including his mistress. During that time, Agatha was already a mentally wreck due to the death of her beloved mother and she could not take it anymore. On the same day, shortly after 9.30 pm, she got up from her favourite armchair, went upstairs to remove her wedding ring, kissed her seven year old sleeping daughter Rosalind and left her with their maid. Then she left her home in Sunningdale and drove off her Morris Cowley into the night towards Surrey. She would not be seen again for eleven days.
Agatha's disappearance sparked a huge manhunt by thousands of policemen and eager volunteers. Even airplanes were also involved in the search. The Home Secretary, William Joynson-Hicks, urged the police to take every possible step to make quick progress in the matter. The Police sought help from two eminent British crime writers Sir Arthur Conan Doyle and Dorothy L. Sayers for their specialist knowledge. Arthur Conan Doyle, a keen occultist, tried using paranormal powers to solve the mystery and took one of Christie's gloves to a celebrated medium. But, it did not work. Dorothy Sayers visited Christie's home for possible clues. That too was futile. Both Archie Christie and his mistress Nancy Neale were under suspicion and there were rumours that she had been murdered by her husband, Archie Christie, a former First World War pilot and serial philanderer.
The next morning Agatha's car was found by Surrey Police on a steep slope at Newlands Corner near Guildford. However, there was no sign Agatha Christie, while a fur coat and a driving licence were left inside the abandoned car with its headlights on. There was a natural spring, the Silent Pool, very near to the scene of the car accident and two young children were reported to have drowned in the pool. In a desperate attempt, the pool was searched by the divers. However, her body was nowhere to be found. Two railroad porters claimed that they spoke with her sometime after her disappearance. She was apparently confused and was seen getting onto a train. However, that was the end of the clue.
During the second week of the search, the news of Agatha Christie's mysterious disappearance had spread like wild fire around the world. Even it made the front page of the prestigious 'New York Times'.
Eleven days after her strange disappearance, Agatha Christie was finally located on the 14th day of December. She was found safe in a hotel in Harrogate. But, how and why she went there and what happened between the 3rd and the 14th of December 1926 is really unknown. Christie herself could not provide any clue as she remembered nothing. Later, during an interview in 1928 with The Daily Mail about the incidents on 3rd December, Christie reportedly said that, on that particular spot she turned off the car, left the wheel and let the car run the road down the hill. Soon the car struck something, while she was flung against the steering wheel and her head hit something. After that, she remembered nothing.
According to the police, after crashing her car, she probably boarded a train to Harrogate. There, at the spa town, she checked into the Swan Hydro, now known as the Old Swan Hotel, without any luggage, under the assumed name of Theresa Neele, her husband's mistress. However, she behaved normally in the hotel and joined in with the balls, where she was eventually recognized by one of the hotel's banjo players, Bob Tappin. Immediately, the police was informed about the startling news that a lively and outgoing South African guest by the name of Theresa Neale may actually be the missing writer in disguise.
On being informed, Archie travelled with the police to Yorkshire and took a seat in the corner of the hotel's dining room. Soon, he found Agatha walked in the room, took her place at another table and begin reading a newspaper which heralded her own disappearance as front page news. When Archie approached by her, he noticed a general air of puzzlement and little recognition in her expression. It was evident that, she could not recognize the man to whom she had been married for nearly 12 years.
Later, her husband said that she had suffered a total memory loss as a result of the car crash. But her biographer, Andrew Norman maintained that, she may well have been in a psychogenic trance, a rare condition brought on by trauma or depression. Her adoption of a new personality under the name of Theresa Neele and her failure to recognize her own photograph in the newspaper were clear indications of psychogenic amnesia.
Archie Christie's declaration about her suffering from amnesia and a possible concussion was later corroborated by two doctors. Soon after the event, Archie and Agatha were divorced. Archie married Nancy Neale and Agatha started her new life in 1930, when she married archaeologist Sir Max Mallowan, who was fourteen years her junior. However, no one involved ever spoke of the disappearance again.
Agatha made no mention of her strange disappearance in her autobiography which was published posthumously in November 1977. And so, the most intriguing and immaculate of all of Christie's mysteries remains unsolved forever. Agatha Christie, the queen of crime and mystery has left a puzzling mystery, a great question mark that probably Hercule Poirot or Miss Marple would have been unable to solve.