During World War II, as submarines scour the Atlantic and American shipping comes under constant threat, an audacious plan unfolds to grind Nazi espionage to a halt. FBI agent G. B. Fleming Roger Pryor suspects that radio signals are tipping off German and Japanese forces to ship movements, and he proposes a sharp, disarming tactic: prune the pool of potential informants by firing all local radio specialists, then shadow the jobless to uncover who among them is secretly loyal to the enemy. The scheme hinges on catching traitors through their own hunger for work, and it sets the stage for a tense cat-and-mouse chase across a coast riddled with danger.
At the heart of the story is engineer Lewis J. "Lew" Deerhold Richard Arlen, a man wrestling with the sense that his own career has stalled because he is a Canadian citizen. Lew is devoted to his young niece Tina Patsy Nash, a war orphan who needs a life-saving brain operation, and this personal pressure pushes him to take chances he might otherwise avoid. Seeking work to support Tina, Lew lands at a radio repair shop where fate introduces him to Ann Patterson Wendy Barrie, a perceptive woman who has just helped someone in trouble after a purse snatching incident. The encounter sparks a cautious trust between them, and Ann’s instincts soon point her toward Lew as someone who could be more than just a neighbor or a neighborly repairman.
Lew’s new world collides with a shadowy conspiracy when his skeptical first impression meets the suave and dangerous Dr. Arthur Huneker Nils Asther and his cunning associate Vincent Bela Marc Lawrence. Huneker, a Nazi spy commander, needs someone with the technical skill to repair a top-secret stolen radio transmitter, and Lew’s expertise makes him a valuable — and dangerous — target. Ann, assigned to shadow Lew, discovers blueprints for the very transmitter in his possession, and when FBI agent Freddie Grayson Ralph Sanford arrives and is shot, the truth leaks out in a rush: Huneker and his cohorts have already laid their hands on the transmitter, and the clock is ticking.
The tension sharpens as the conspirators press Lew to join their cause. They attempt to recruit him in a chilling scene that also brings in Commander Toyo Abner Biberman, a Japanese officer who represents the other face of the alliance between the Nazis and the Japanese. The plot thickens when the group manipulates Bambridge, the owner of the Bambridge shipping company, with the disturbing revelation that Bambridge is really Captain Haigas, an American agent hidden behind a veneer of corporate respectability. The stakes rise as the newly recruited “traitor” in their midst rebels, managing to escape with the codes to the transmitter and the chance to turn the tables on his pursuers.
Lew and Ann refuse to abandon the fight. They slip away from Huneker’s clutches, but not before their pursuers tighten the net, eventually dragging them to a remote hot springs resort where they’re trapped in a steam room. The minute-by-minute danger escalates as Huneker and his minions move to finish the job—yet Lew, driven by a mix of duty, fear, and a stubborn sense of justice, engineers a clever countermeasure. He constructs a working transmitter while the heat of the room rises, and he sends out an SOS just as the steam threatens to seal their fate. The message is picked up by a diligent boy whose father immediately alerts the FBI, triggering a rapid, coordinated response.
The operatives closest to the case rally to save Lew and Ann, and in a swift culmination, Huneker and his network are arrested. Agent Fleming coordinates with a bomber squadron to neutralize the danger beyond the coast, destroying the Japanese submarine that had been waiting to strike off California. The immediate danger recedes, and the film closes on a note of cautious relief: Tina’s operation is successful, Lew’s aunt-like care for his family bears fruit, and, in a moving turn of events, Lew becomes a private in the U.S. Army and finally earns American citizenship, their small triumph echoing the larger war effort.
This story blends espionage, perseverance, and personal sacrifice into a tightly wound wartime thriller, where every action is a step toward protecting families, ships, and nations. The performances—anchored by Lew’s steadfast resolve, Ann’s conscientious skepticism, Huneker’s chilling menace, and the steadfast courage of those who stand against tyranny—deliver a narrative that stays true to its wartime roots while exploring the moral complexities of loyalty, identity, and sacrifice.
