It has been noted in Sir Max Mallowan's memoir that the setting of Dead Man's Folly is based on Greenway House, a property bought by Christie and her husband in 1939. The boathouse and river attached to the fictional Nasse House are both features borrowed from Greenway House.
Dead Man's Folly begins when Hercule Poirot gets a call from his friend, Ariadne Oliver, the famous detective story writer who always gets mixed up in murder cases. This time, she has been invited to Nasse House in Devon to organise of one of the events in a local charity show. The show is an annual tradition, organised by the owner of the house to let the local people enjoy themselves, and features fortune-telling, handcraft stalls, a food …
Lee, Amy. "Dead Man's Folly". The Literary Encyclopedia. First published 11 August 2003
[https://www.litencyc.com/php/sworks.php?rec=true&UID=5719, accessed 22 March 2018.]