Hercule Poirot attends a London supper party where the beautiful American actress Jane Wilkinson, now Lady Edgware, openly speaks of wanting to be rid of her cold, estranged husband so she can marry the Duke of Merton. She enlists Poirot to persuade Lord Edgware to grant a divorce, and to the detective's surprise the disagreeable peer agrees at once, claiming he has already written to consent. Soon afterward Lord Edgware is found stabbed to death in his study, and every clue points to his wife. Yet Jane has an unbreakable alibi: a dozen reputable witnesses swear she dined across town at the very hour of the killing. The case deepens when a gifted young impressionist, fresh from a celebrated stage turn, is also found dead. Working alongside Captain Hastings and Inspector Japp, Poirot confronts an apparent impossibility, a household full of resentments, and a tangle of false faces and borrowed identities. With his usual insistence on order, method, and the small revealing detail, Poirot must sort genuine alibi from clever performance and untangle who profited from the death of a much-hated man. The puzzle hinges on appearances, on who was truly where, and on a remark dropped at a dinner table that no one but Poirot thinks to weigh.