In an effort to beguile their Devonshire neighbours, wealthy financier SIR GEORGE STUBBS and his 'subnormal' wife HATTIE prepare to stage a grand summer fete in the grounds of their new acquisition, Nasse House. No expense is spared, and the lawn is soon bustling with visitors keen to have their fortune told, to compete in the fancy dress and to try their hand at the coconut shy. And then there is the ultimate challenge: a fiendishly complicated 'murder hunt' prepared by the famous mystery novelist ARIADNE OLIVER. But Ariadne is perturbed. Convinced that someone is 'jockeying her along', she insists on the presence of her old friend HERCULE POIROT, who reluctantly agrees to apply his uniquely analytical mind to a crime that, as yet, only exists in Ariadne's imagination. The denizens and friends of Nasse are certainly an awkward and pernicious bunch: Poirot soon encounters the local Member of Parliament CAPTAIN WARBURTON and his imperious wife MRS WARBURTON, squabbling holidaymakers ALEC and SALLY LEGGE, lecherous architect MICHAEL WEYMAN, rambling ferryman JOHN MERDELL and the fete's uninvited guest, urbane foreigner ETIENNE DE SOUZA. And then there is AMY FOLLIAT, once the proud owner of Nasse, and now Sir George's pauperised lodger. Any one of them could be the killer; any one of them could be the victim. But what actually happens is utterly bewildering. Girl guide MARLENE TUCKER - volunteer actor in Ariadne's murder hunt - is found strangled to death in the secluded boat house. It seems like a motiveless act; but of course it is not. As Poirot and Ariadne try to pick their way through Nasse's web of secrets and lies, another mystery presents itself - the vanishing of vulnerable Hattie Stubbs. Where is Hattie? Who killed Marlene? Who really authored Ariadne's murder hunt? What is the significance of Sir George's ghastly folly? And can it be true that this is a mystery the great Hercule Poirot cannot solve?