The enigmatic, sinister Mr. Shaitana, one of London's richest men, invites 8 guests, 4 of them possible murderers and 4 'detectives' to his opulent apartment.
A young widow is left in sole possession of her late husband's fortune, her brother who dominates her refuses to let her share it with her in-laws, so they enlist Poirot to prove her missing first husband might not be dead.