Investigating a murder the night before Christmas, Hercule Poirot finds the tyrannical, aging millionaire in his locked room, dead. He also finds the man's relatives, all of whom suspect each other. Poirot must put his deductive powers to the test to solve one of his most chilling cases – and to prevent a clever killer from spilling more blood. 19th in the series. "Never has Poirot's mighty brain functioned more brilliantly."—The New York Times