13 Rue Madeleine

Bob Sharkey is put in charge of a group of American espionage candidates. His boss, Charles Gibson, reveals that one student is a German Abwehr agent. Sharkey accepts the challenge to identify the double agent and bring the deception to light.

Sharkey correctly identifies the student using the alias Bill O'Connell as Wilhelm Kuncel, one of Germany's top spies. Gibson confirms the identity and the real mission begins to unfold. Sharkey prepares to oversee the deception and plan around this discovery.

Kuncel is posted to London to access and relay false information about Plan B, the invasion strategy. The aim is to mislead German intelligence through controlled data. Sharkey's team uses this placement to feed deceptive material back up the chain.

Lassiter is assigned to kidnap the French collaborator Duclois and bring him to England. De Beaumont accompanies as Lassiter's radio operator. O'Connell remains in London with access to the bogus intel, while the operation is orchestrated to undermine Southampton's V-2 rocket capabilities.

Gibson warns Lassiter that he must kill Kuncel if he suspects the double agent has not been deceived. The instruction is a precaution to prevent the spy from revealing the truth. The plan hinges on maintaining the deception until the mission reaches its critical stage.

During the airplane mission, Lassiter grows uneasy, and Kuncel realizes he is suspected. Kuncel sabotages Lassiter's parachute, causing him to fall to his death. Sharkey's team is left without the intended agent to carry out the operation.

Back in Britain, Gibson and Sharkey determine that Kuncel now knows the information supplied to him is false. The deception plan has been compromised by Lassiter's death. They must pivot quickly.

With no time to brief another agent, Sharkey volunteers to take Lassiter's place in the mission. Gibson is reluctant but agrees. Sharkey assumes the dangerous role, hoping to salvage the operation.

Sharkey, aided by the local French resistance led by the town mayor, captures Duclois to secure the V-2 depot intel. The capture is part of the broader plan to disrupt German rocket production. They prepare to fly Duclois to England for interrogation.

As the airplane departs with Duclois, Kuncel attempts to interfere with the mission. Sharkey prevents interference, but in the process he is himself captured by the Gestapo. The escape route is cut off, jeopardizing the mission.

De Beaumont is killed while transmitting news back to England about the operation. Her death highlights the price paid by the resistance and the mission's risks. The loss compounds the tension among the remaining operatives.

Kuncel escorts Sharkey to Gestapo headquarters at 13 Rue Madeleine in Le Havre. He subjects Sharkey to torture as he refuses to reveal information. The interrogation underscores the Germans' determination to uncover the truth.

Back in Britain, Gibson has no choice but to order a bombing raid to destroy the building before Sharkey cracks. The raid aims to thwart the torturer and prevent leakage of the true invasion date. The operation reveals the desperation to maintain deception.

As bombs fall, Sharkey laughs in triumph at Kuncel's face, convinced he has prevailed over the deception. The false information remains intact as the building is destroyed. The scene caps the tense cat-and-mouse game between double agents.