Dead Man's Folly
Agatha Christie
 En route to Nasse House, Poirot gives a lift to two female hitch-hikers – one Dutch and one Italian – who are staying at the youth hostel adjoining the Nasse House grounds. When he arrives, Mrs Oliver explains that she feels that her plans for the Murder Hunt have been, almost imperceptibly, influenced by the advice that she has been given by people in the house, until it is almost as though she is being pushed into staging a real murder. The owner of Nasse House is George Stubbs, a wealthy man who has seemingly adopted an unearned title of "Sir" in order to confirm his position in the local community. His much younger wife is the seemingly simple and impressionable Hattie, a young woman who has apparently been introduced to him by Amy Folliat, the surviving member of the family that once owned the house. Now that her sons have been supposedly killed during the War, she is living out her days in the Lodge House. Other visitors at Nasse House include an architect, Michael Weyman, who criticises the siting some years earlier of a folly in an inappropriate area of the grounds. On the day of the fête, Hattie learns that a cousin, Etienne de Sousa, is about to visit, and she seems upset by this, referring to him as a killer. At the fete, a local Girl Guide, Marlene Tucker, is to play the part of the victim, and she waits in the boathouse to play her role when someone approaches her. Poirot observes the movements of some of the visitors to the house. Later, in the company of Mrs Oliver, he discovers the corpse of Marlene in the boathouse. Moreover, Hattie is discovered to have gone missing. Both the police and Poirot himself are initially baffled. The investigation focuses on Etienne de Sousa, a wealthy young man who shows no apparent concern at Hattie’s disappearance and has arrived in perfect time to have committed the murder. Another suspect is Amanda Brewis, George's secretary, who appears to be in love with Sir George and claims to have been sent down to the boathouse by Hattie with refreshments for Marlene at around the time that the girl was killed. This sounds very out of character for Hattie. Further confusion is added by the behaviour of the Legges, who appear to have some sort of shady connection with a young man in a turtle shirt who has been seen in the grounds. (It later comes to light that this red herring is connected with Legge's career as a nuclear physicist.) Poirot’s attention is directed to Amy Folliat, who seems to know more than she is saying. After the boatman Merdell dies, Poirot discovers that he was Marlene’s grandfather. Now he puts together several stray clues: Marlene had said that her grandfather had seen someone burying a woman in the woods; Marlene was the type to blackmail, and had in fact received small sums of money prior to her murder; Merdell had commented significantly to Poirot that there would "always be Folliats at Nasse House". In the denouement Poirot reveals that "Sir" George Stubbs is none other than Amy Folliat's younger son, James, who had deserted during WWI. Instead, Amy had paired him with the impressionable, but very wealthy, Hattie, hoping they would make a good couple. However, he fleeced her of her money and established his new identity, buying the family house and ensuring the continuity of Folliat possession. Unbeknownst to his mother, however, George/James was already married, and as soon as he had possession of Nasse he killed Hattie, and substituted his legal, first wife, a young Italian woman, in her place. The real Hattie was buried on the grounds where the Folly was built. Marlene Tucker had guessed the secret from hints dropped by her grandfather, and George and his real wife decided it would be safer to kill her than continue giving her hush money. The day before the day of the murder, "Hattie" began to establish another identity as an Italian hitch-hiker. On the day of the murder, she switched between the two roles, killing Marlene and leaving the grounds as the hitch-hiker, with Hattie's clothes in her rucksack. The day of the murder had been selected to cast suspicion upon Etienne, who had actually notified them some weeks earlier of his visit, of whom the fake Hattie pretends to be afraid. As Hattie's cousin, Etienne would not have been deceived and would have realized that the fake Hattie was not his cousin. The arrests of the culprits is not referenced in the novel, the end of which focuses on the despair of Amy Folliat, who does not appear to be facing legal charges, although that is never quite spelled out, in her allocution to Poirot.