Hercule Poirot and Inspector Edward Catchpool are looking forward to Christmas when they are called upon to investigate the murder of a man in a Norfolk hospital ward. Cynthia Catchpool, Edward’s mother, insists that Poirot stay with her in a crumbling mansion by the coast so they all can be together for the festive period while he solves the case. The local constabulary’s investigation failed to uncover how someone could have entered a hospital room and killed him under the noses of the staff. Cynthia’s friend, Arnold, is soon to be admitted to that same hospital, and his wife is convinced he will be the killer’s next victim, though she refuses to explain why. Meanwhile, an utterly ruthless individual has ideas about what ought to happen to Hercule Poirot.