Hercule Poirot, contemplating retirement, falls into conversation with his old friend Dr Burton, a classics scholar, who teases him about sharing a name with the hero of Greek myth. The detective, who knows little of his mythological namesake, reads up on the ancient Hercules and is privately appalled by the brawling brute he finds in the legends. Yet the structure of the Twelve Labours appeals to his sense of order, and he resolves on a conceit: before he hangs up his practice for good, he will accept exactly twelve final cases, each chosen to echo one of the labours. What follows is twelve linked stories, every one matched to a labour from the Nemean Lion to the capture of Cerberus. The parallels are playful and often ironic rather than literal, a kidnapped Pekinese stands in for the lion, malicious gossip becomes the many-headed hydra, so that the mythic scaffolding lets Christie range across blackmail, poisoning rumours, missing persons, drug rings, and quiet domestic menace. Poirot works mostly alone here, applying method and psychology to small human crimes dressed in heroic costume. The tone is lighter and wittier than the full novels, with the detective treating each commission as a self-imposed test of his own legend. The final case reunites him with an old adversary and brings the scheme, and a phase of his career, to a deliberate close.