Poirot: The Affair at the Victory Ball (1991)

Poirot attends the Victory Ball, a costume party where you are expected to dress as someone famous, as himself. However, when two members of a party of six dressed as characters from classical Italian comedy are subsequently found dead, Poirot finds himself working with Chief Inspector Japp to solve the case. The solution to the deaths of Viscount Cronshaw and Coco Courtney is to be found in determining the correct time of death and identifying an impostor at the ball. Poirot takes to the airwaves and reveals the identity of the killer on a live BBC radio broadcast.