Richard Hannay (Kenneth More) is in the wrong place at the right time when he saves the life of a nanny, who has no baby to take care of. She reveals to Hannay that she is in fact a spy with British Intelligence, looking for the leader of "the Thirty-Nine Steps," a group that is in possession of top-secret missile plans. Hannay leaves the room, and she is killed by two hit men. Afraid that he will be accused of murder, Hannay is forced to go on the run, attempting to escape the assassins at all turns. He also adopts the mission of the slain spy as his own, trying to discover the truth about the Thirty-Nine steps. Along the way, Hannay is joined in his journey by Miss Fisher (Taina Elg), a teacher at a girl's boarding school who becomes equally mixed-up in the intrigue.