An ailing Poirot returns to Styles with Hastings nearly three decades after solving their first mystery there in order to prevent a serial killer from claiming more victims.

Poirot's pursuit of an infamous art thief leads him to a snowbound hotel in the Swiss Alps, where he is met with a plethora of mysteries and the reappearance of a familiar face from the past.

Mrs. Oliver is asked to devise a murder hunt for a Devon fête, but her sense of foreboding summons Poirot to the scene. Her fears are realized when the girl playing murder victim winds up truly murdered.

As the threat of world war looms large, Poirot seeks the help of friends both old and new when he is pitted against a dangerous group of dissidents responsible for a series of violent murders.

Ariadne Oliver becomes an amateur sleuth when her goddaughter tasks her to find out the truth behind her parents' mysterious deaths.