England mourns the loss of war hero and famed novelist Edgar Brodie as this tangled spy mystery begins. The only problem is that Brodie (John Gielgud) is among the last to know. Returning from the war, he discovers that he has been declared dead, singled out for a new identity, and given a special assignment that will include his new "wife," Elsa (Madeleine Carrol). They are joined by the cool and deadly hit man the General (Peter Lorre) and also pick up the talkative gadfly American Robert Marvin (Robert Young). From the start the mission goes awry as the trio of British agents discover their local informant dead, with a button clenched in his hand the only clue to who killed him. As they struggle to complete their mission a complex love tangle develops with Robert and the General competing for Elsa's affections as she gauges Brodie's indifference. Each follows his or her best instincts, setting up the dramatic climax.