Union Station

Joyce Willecombe approaches Lieutenant Bill Calhoun at Chicago Union Station, convinced two men aboard her train may be up to no good. Bill takes the warning seriously and begins monitoring the area for any signs of trouble. The station becomes the focal point of an unfolding kidnapping case.

Two men deposit a suitcase in a storage locker at the station, setting the trap for a ransom scheme. When Bill retrieves the suitcase, Joyce recognizes clothing belonging to Lorna Murchison, the kidnapped daughter of Henry Murchison. Mr. Murchison is brought in and admits Lorna has been kidnapped and demanded for ransom, but he resists police involvement; Bill and Donnelly persuade him to accept their help.

Mr. Murchison confesses that the kidnapping is real and that a ransom is demanded, but he wants to avoid police involvement to protect his daughter's safety. Bill and Inspector Donnelly pressure him, ultimately persuading him to allow law enforcement to assist. The decision marks a turning point in the case as officers finalize their plan.

With the plan in motion, the station is chosen as the ransom payoff site, allowing the police to monitor the exchange. Bill and Donnelly race against time to coordinate the handoff and track the kidnappers before Lorna is harmed. The tension builds as every minute counts.

During the ransom contact at the station, Joyce spots the suspects, confirming their identities. The pursuit leads to Gus Hadder, who spots the police and runs, ultimately dying in an accident; authorities suppress the death from newspaper reports to avoid drawing attention.

Joyce later identifies Joe Beacom, the gang leader, and also sees Vince Marley, a second kidnapper. Marley is arrested after refusing to talk, while Beacom drives away; Joyce memorizes Beacom's license plate for future use.

Donnelly instructs Bill to kill Marley and make it look accidental, hoping the lack of a confession will force a reveal. The officers stage a fake execution by throwing Marley before an arriving train, but Marley cracks and tells them where Lorna is being held.

Beacom and his girlfriend Marge Wrighter have already taken Lorna somewhere else by the time the police break in, complicating the search. Joyce remains vigilant, trying to glean Lorna's whereabouts from any clue. The plot tightens as the criminals move Lorna further from the station.

A patrolman spots Beacom's car and a gunfight erupts, leaving a policeman dead and Wrighter fatally wounded. The wounded Wrighter is hospitalized and provides crucial information about Beacom's plans. Her testimony ties Beacom's movements to the raid and clarifies his intent regarding Lorna.

In the hospital, Wrighter reveals that Beacom intends to kill Lorna after the ransom and notes that Beacom previously worked at the station, lending him access. The revelation helps the police piece together Beacom's method and motive.

Beacom, dressed as an employee, forces a parcel clerk to accept the ransom and switch it with a decoy, while the messenger who brought the first package is instructed to move the second suitcase elsewhere. Joyce catches part of a coat sticking out of the decoy, a crucial clue.

Bill tries to stop Beacom and is shot in the shoulder, but Beacom heads to the municipal tunnel beneath the station with Lorna. Bill pursues through the tunnel and finally shoots Beacom, killing him and rescuing Lorna.