The Sign in the Sky — Agatha Christie

Previously published in the print anthology The Mysterious Mr. Quin.

Mr. Satterthwaite attends the trial of young Martin Wylde, accused of murder. Shortly after the guilty verdict is returned, Satterthwaite runs into his mysterious friend Harley Quin. Can they prove Wylde's innocence, or did he really kill the beautiful Vivien Barnaby?