London, 1949. A young American beauty, Melinda Greyton, flighty and immature, falls in love with a dashing but solitary and lonely English major, Michael Curragh, and he with her. His aged aunt, his only family, urges him to marry her, and he does. The trouble is, he's an agent for the Soviets. His control is unhappy that he's married without the Party's consent. Melinda figures out he's a spy and a traitor, and she develops some backbone and maturity when he tries to convince her to go along with him. She demands that he cease spying at about the same time that his control orders him to kill her. Is she safe? Is there any way he can satisfy conflicting loyalties?