Arthur Rowe, a middle-aged Englishman, finds himself at a country fair in London during the Blitz, seeking a glimpse of better times. While exploring the fairgrounds, he visits a fortune-teller who reveals the exact weight of a cake, promising it to whoever guesses correctly. With surprising accuracy, Rowe wins the cake, but a clergyman overseeing the event attempts to reclaim it. Refusing to comply, Rowe donates a pound and leaves the scene with his prize.

An Unexpected Visitor

That night, as German bombers approach, an unusual visitor appears at Rowe's door, a tenant in the same building. Acting suspiciously, the man crumbles a piece of cake Rowe offers him, seemingly searching for something hidden inside. When Rowe briefly steps out, the visitor poisons his tea. Rowe returns just in time to notice the odd scent and, before taking action, a bomb detonates nearby, destroying the house. Dazed, Rowe awakens amidst the rubble, his home in ruins.

Seeking Answers

In the aftermath, Rowe, haunted by his past involving the mercy killing of his wife, is left with few allies. Desperate for help, he engages a detective named Jones to unravel the mystery behind the attempt on his life. His investigation leads him to the relief office responsible for the fair, where he meets Anna Hilfe and her brother, Willi, claiming to be Austrian refugees. Together, Rowe and Willi visit the fortune-teller's home, hoping to uncover the truth.

Séance Turned Sinister

Their visit coincides with a séance, and as the event unfolds, the man next to Rowe is murdered with Rowe's own knife. Chaos ensues, and with Willi's assistance, Rowe escapes before the authorities arrive. Seeking refuge in an air-raid shelter, Rowe drafts a letter to the police. However, Anna warns him over the phone that "they," a group of Nazi agents, still pursue him. Bewildered by his predicament, Rowe sends her an address for contact.

Disappearing Detective

Rowe's next call to the detective agency reveals that Jones has vanished, and the agency has notified the police. Lost in thought, Rowe roams the city until he encounters a stranger who requests him to deliver a suitcase of books to Mr. Travers at a hotel. Upon arrival, Rowe is led to a room where Anna awaits. With air raids looming, they fear that the Nazi agents will seize the opportunity to kill them amid the chaos. A bomb strikes the hotel, leaving Rowe unconscious.

Fragmented Memories

Rowe awakens in a private nursing home, his memory fragmented, retaining nothing beyond his eighteenth year. Anna visits him frequently, and Rowe's affections for her grow. She avoids revealing his past, insisting Dr. Forester, the institution's head, prefers a gradual recovery to prevent shock. A soldier confides in Rowe about mysterious digging on the grounds, resulting in his immediate restraint, while Rowe is confined, ostensibly for a relapse.

The Escape

Suspicious of sinister activities, Rowe sneaks out to see the soldier, confirming his fears. When Dr. Forester confronts him angrily, threatening a straitjacket, Rowe escapes with an attendant's help and turns himself in at Scotland Yard, confessing to the séance murder. To his astonishment, the police reveal no murder occurred; it was a ruse to drive him into hiding, and the nursing home is a cover for espionage activities.

The Deceptive Tailor

Accompanied by a counterintelligence officer, Rowe visits the presumed murdered man's tailor shop. Their interview is cut short when the tailor makes a phone call and subsequently takes his own life. Frustrated by the dead end, the officer explains Rowe unwittingly received a cake containing secret film, stolen by Nazi agents. Continuing their investigation, they...