The Big Four plunges Poirot into a world of global espionage, set against the backdrop of the impending WWII. The public is in a panic after the shocking death of a Russian chess grandmaster at the climax of a high-profile international Peace Party reception. With the help of old friends Captain Hastings, Inspector Japp and Miss Lemon, Poirot must make a dramatic move that only a chess champion could love, while navigating international figures and intrigues in order to identify the culprit.