The Big Four is a work of detective fiction by Agatha Christie and first published in the UK by William Collins & Sons on January 27, 1927 and in the US by Dodd, Mead and Company later in the same year. It features Hercule Poirot, Arthur Hastings and Chief Inspector Japp. The UK edition retailed at seven shillings and sixpence (7/6) and the US edition at $2.00.
The structure of the book is different from that of most Christie novels in that The Big Four is a series of short cases involving the Big Four villains rather than the investigation of a single crime. This is due to the fact that it is derived from a series of linked short stories that first appeared in The Sketch magazine (see First publication of stories below) and which were amalgamated into one narrative.