The Affair at the Victory Ball

Inspector Japp asks Hercule Poirot to assist Scotland Yard in the strange events which took place at a recent costumed Victory Ball. A group of six people, headed by the young Viscount Cronshaw, attended all dressed in the costumes of the Commedia dell'Arte. Lord Cronshaw was Harlequin, his uncle, the honourable Eustace Beltane, was Pulcinella. In the roles of Pierrot and Pierrette were Mr and Mrs Christopher Davidson and finally, Miss "Coco" Courtenay, an actress rumoured to be engaged to Lord Cronshaw, was Columbine. During the ball, Cronshaw was stabbed through the heart with a table knife. The next morning Coco Courtenay was found dead in her bed from an overdose of cocaine.

Poirot deduces that, since rigor mortis had set in by the time Cronshaw's body was discovered, the person seen in the Harlequin costume not long before the body was found must have been one of the others. Poirot reveals that the strength with which the knife was plunged into Cronshaw meant that a man was responsible for the crime. He identifies the killer as Christopher Davidson, whom Cronshaw was about to expose as Coco's drug supplier. Davidson killed Cronshaw, hid the body behind a curtain, then took Coco home and gave her enough cocaine to kill her. He returned to the ball, stripped off his Pierrot costume to expose a Harlequin one underneath, and impersonated Cronshaw to throw off suspicion.