Dead Man's Folly is a work of detective fiction by Agatha Christie, first published in the US by Dodd, Mead and Company in October 1956[1] and in the UK by the Collins Crime Club on 5 November of the same year.

Poirot is invited to Nasse House in Devon by crime-mystery writer Ariadne Oliver, who is staging a Murder Hunt as part of a summer fête the next day.

Michael Weyman, an architect, is on site to design a tennis court; he criticises the inappropriate location of a recently built folly.

A local Girl Guide, Marlene Tucker, waits in the boathouse to pose as the dead victim when a player finds the key to enter.

In the dénouement, Poirot explains that Sir George Stubbs is really Amy Folliat's younger son, James, a war deserter.

The date of Marlene's murder had been selected to cast suspicion upon Etienne, who had written weeks earlier of his visit, as he told Inspector Bland.

As the sounds of the police smashing up the folly to locate and exhume Hattie's body are heard, Mrs. Foliat asks Poirot to go away so she may face things alone, leaving the fate of herself and her son ambiguous.

Poirot is on hand with his superb English, based, one supposes, on the middle line in the French lessons in the Children's Encyclopaedia, but the little grey cells are rather subdued."

He set up the basics of the plot and then continued, "The solution is of the colossal ingenuity we have been conditioned to expect but a number of the necessary red herrings are either unexplained or a little too grossly ad hoc.

"[5] Maurice Richardson of The Observer (18 November 1956) pointed out the similarity between the house portrayed in the book and Christie's own and summed up, "Stunning but not unguessable solution.

"[7] The novel was made into a film with Peter Ustinov and Jean Stapleton starring as Poirot and Oliver in a 1986 adaptation set in the present day.

John Moffatt starred as Poirot in the BBC Radio 4 dramatisation broadcast in 2007, with Julia McKenzie as Ariadne Oliver.

[9][10] The telefilm was shot mainly at Agatha Christie's home, Greenway Estate, the setting she used, along with its old boathouse on the River Dart, for the novel.

Mrs Masterton becomes Mrs Warburton, Captain Warburton's wife; Marlene's sister, Marilyn, becomes an older sister named Gertie, but serves the same function as Marilyn in the novel; the characters of George the valet, Miss Lemon, the man in the turtle-printed shirt, and Marlene's parents are deleted.

On 15 October 2009, I-play released a downloadable hidden object game based on Dead Man's Folly (see the external links).