On a visit to post-war Berlin to see her brother and his German wife Bettina, Susanne Mallison becomes aware of the mysteries and tensions that surround her sister-in-law. Things become clearer when Bettina reluctantly takes Susanne into the Eastern Sector. There they meet Ivo Kern, a one-time lawyer who is being blackmailed into luring a man called Kastner into East Berlin. Kastner is helping refugees escape to the West. When she finds that Susanne is attracted to Kern, Bettina makes a startling confession.