Richard Hannay is at a London theatre, attending a demonstration of the remarkable powers of “Mr. Memory”, a man with a photographic memory, when a fight breaks out and a shot is fired. In the ensuing panic, he finds himself holding a frightened Annabella Schmidt, who talks him into taking her back to his flat.
There, she tells him that she is a spy, being chased by assassins out to kill her. She claims to have uncovered a plot to steal vital British military secrets, implemented by a man who is the head of an espionage organization called “The 39 Steps.”