Crime novelist Ariadne Oliver has been engaged to devise a Murder Hunt, a treasure-hunt-style game, for a summer fete at Nasse House, a grand estate on the Devon coast. As preparations proceed, she grows uneasy: small details keep shifting in ways she did not intend, as though an unseen hand is steering events. Trusting her instinct that something genuinely sinister is taking shape, she telephones her old friend Hercule Poirot and asks him to come down, ostensibly to present the prizes. Poirot arrives to find a household of guests and locals each absorbed in their own concerns, and a game whose staged corpse is to be played by a teenage Girl Guide hidden in the boathouse. When the fete opens and the hunt begins, the pretend victim is discovered genuinely dead, and another person connected to the estate vanishes without trace. Poirot must untangle the careful arrangements of the game from the design of an actual killer, sifting the history of the house and its former family from the strangers now living within its walls. Working alongside Mrs Oliver and the local police, he weighs the alibis of weekend visitors, estate staff, and villagers, testing which coincidences are real and which were manufactured. The investigation turns on questions of who people truly are and what the land itself has long concealed, drawing on identity, inheritance, and the quiet weight of the past.