Arthur Rowe, a middle-aged Englishman living through World War II in London. He is a lonely widower, having killed his wife to prevent her living in pain. By accident, he comes into possession of secret films taken by Nazi agents, and he immediately becomes the object of their search. He suffers amnesia when injured in a bombing raid and is unable for a time to remember anything beyond his youth. He finds himself confined in a nursing home that is a front for Nazi activities. He escapes and, aided by counter-intelligence agents, uncovers the Nazi activities. He regains his memory at the same time. Meanwhile, he has fallen in love with Anna Hilfe, sister of the spy group’s leader.
Mr. Jones, a private detective. He is hired by Rowe, who wants to know why someone wants to kill him. Jones disappears, and his employer turns the case over to counter-intelligence.
Anna Hilfe, a young Austrian refugee. She informs Rowe that Nazi agents are after him. Though her brother is a Nazi spy, she helps Rowe uncover the enemy activities because she has fallen in love with the Englishman.
Willi Hilfe, an Austrian refugee, Anna’s brother. He helps Rowe “escape” when a man is supposedly murdered. Hilfe turns out to be the head of a Nazi fifth-column group operating in England. He commits suicide when he is found out.
Dr. Forester, head of the nursing home in which Rowe finds himself. Forester, an enemy agent, is killed by one of the hospital attendants.