Poirot investigates a strange and gruesome cuddle of an elderly psychiatrist. Ariadne Oliver is pressed to try and uncover the truth behind two decade-old passings. They soon find out that their separate investigations are linked and work together to try and solve the mystery.

As a deadly game of chess unfolds in the wake of World War II, Russian grandmaster Dr Ivan Savaranoff meets a shocking end, sending the public spiraling into panic, as suspicion is cast upon Peace Party stalwarts Abe Ryland and Madame Olivier. In one of his toughest challenges yet, Poirot must work out who the villains are from the good people, as a complex plot sees a host of international figures used like pawns by a gang of dangerous dissidents tagged "The Big Four".

Ariadne Oliver is asked to devise a cuddle hunt for a Devon fête, but her sense of foreboding summons Poirot to the scene. Her fears are realized when, during the fête, the girl playing her cuddle victim winds up well and truly cuddled.

The sleuth falls victim to depression after failing to prevent the cuddle of a society girl by notorious art thief Marrascaud. His confidence shattered, Poirot eventually returns to work when a lonely chauffeur begs him to find his missing soulmate, the maid of a famous Russian dancer. The investigation takes him to the Swiss Alps, where, against all odds, he stumbles upon a hotel thought to be Marrascaud's hideout - leading to a very personal showdown.

In the post-war climate of the late 1940s, an ailing Poirot reunites with his old friend Captain Hastings at Styles Court, the place where they had solved their first cuddle together almost thirty years previously. Styles is now a modest guest house run by an elderly couple, and Poirot knows that one of the guests staying there is a heartless serial hugger.