Set during the Second World War, Stephen Neale (Ray Milland) leaves the Lembridge Asylum after two years as we start the film - we aren't to find out until later why he was in there. While waiting for a train to London, he attends a local charity fête, has his fortune told, and then wins a cake because of something the fortune teller told him. Unfortunately, someone else really wants the cake, and trying to find out what that was about once he gets to London leads him into a tangled mess of problems, up to and including murder. He falls for one of the suspects, a lovely refugee from Nazi Austria who runs a charity associated with the one that produced the troublesome cake.
The original novel of the same name was written by Graham Greene, and the movie was directed by Fritz Lang. I'm not sure it lives up to that legacy, but it was definitely an enjoyable and well put together movie.