Counter-Espionage

In war-torn London, Harvey Leeds, secretary to Sir Stafford Hart, the eminent British criminologist, advocates the immediate arrest of all foreign agents. As he leaves the Hart mansion to join his fiancée, Sir Stafford's daughter, Pamela, who is working at an air raid shelter, Harvey stops in the foyer to rummage through a briefcase owned by Kent Wells, Sir Stafford's assistant. On the street, Harvey is greeted by air raid warden Anton Schugg, who knocks the secretary unconscious and dumps his body in the back of his ambulance. Meanwhile, Kent, who has witnessed Harvey rifling his briefcase, goes upstairs and sees a prowler opening the safe in Sir Stafford's library. The prowler flees with the government's secret beam detector plan, but leaves behind a cufflink with the initial "L" engraved on it. When Scotland Yard is called to investigate, Inspector J. Stephens invites his visiting American counterparts, Inspectors Crane and Dickens, to accompany him to the Hart house. There the inspectors surmise that the cufflink belongs to Michael Lanyard, the notorious jewel thief known as the Lone Wolf. Lanyard, meanwhile, meets his valet Jamison on a London street in the middle of an air raid. When a bombed-out building begins to topple onto air raid warden George Barrow, Lanyard pushes Barrow out of the way and saves his life, earning his gratitude. Jamison and Lanyard take refuge from the bombs in an air raid shelter and there meet Pamela, who is serving the occupants sandwiches while anxiously awaiting Harvey's arrival. When Stephens and the other inspectors enter the shelter, Lanyard takes the stolen plans from his coat pocket and hides them under a plate of sandwiches. After Stephens arrests Lanyard for espionage and takes him away, Jamison retrieves the plans. At Scotland Yard, Stephens is about to interrogate his prisoner when Lanyard grabs a gun from a desk drawer, takes Sir Stafford hostage and flees. On the street, Lanyard is met by Schugg, who offers him a ride in his ambulance. After driving away, Schugg stops the vehicle, blindfolds Lanyard and explains that he is bringing him to listen to a business proposition. In a secret basement headquarters, Lanyard meets Gustave Sossel, a German agent, who offers a large sum of money for the plans. Noting that Sossel is holding Harvey prisoner, Lanyard explains that he will need several days to retrieve the plans. Soon after, Kent enters the basement and informs Lanyard that he ordered Harvey's arrest because the secretary was becoming too curious. After showing Lanyard the radio device over which he intends to broadcast the plans to Berlin, Sossel instructs the thief to contact Schugg once he possesses the plans. Schugg then escorts him back to the street, and there, Lanyard sees a newspaper headline announcing that Sir Stafford has died in an air raid. The next morning, Stephens visits the Hart house, and as the inspector questions Pamela about her father's death, Kent searches Sir Stafford's files and discovers a document commissioning Lanyard to expose and apprehend the enemy spy ring. After Kent pockets the document, Lanyard phones the Hart house, intending to distract the police by allowing them to trace the call to his apartment. As the police go on a wild goose chase to the apartment, Lanyard tries to locate the spies's headquarters by retracing the sounds he heard along the way. When Lanyard and Jamison realize that Pamela is following them, Lanyard tricks her into phoning Stephens so that there will be police reinforcements in the district surrounding the spies's headquarters. To hide from the police, the pair then climb into an ambulance. When the ambulance driver, who is George Barrow's daughter, stops to pick up her father, Barrow climbs into the back and discovers Lanyard hiding there. Believing that Lanyard is innocent, Barrow promises to help and allows them to escape. Lanyard then returns to the spies's neighborhood and, feigning blindness, follows a guidepost of sounds to a basement underneath the Blue Parrot Café, where he is surprised to meet Pamela. German agents, posing as employees of the café, then seize him and Pamela and take them to Sossel. In Sossel's basement hideout, they find Harvey and Kent, who identifies himself as Kurt Weil, a German operative. Tracking Lanyard to the café, the inspectors are escorted at gunpoint to the basement headquarters, where Pamela, Harvey and Lanyard are being held. As Sossel begins to transmit the plans which he has seized from Lanyard, Barrows, summoned by Jamison, arrives, pretending to hold a vial of nitroglycerin in his hand, which he threatens to explode unless the spies disarm themselves. After the spies throw down their guns, Sossel refuses to exonerate Lanyard, who calmly informs him that the transmitted plans were fake. Lanyard then offers to prove his innocence by producing the real plans. Realizing that he has failed in his task, Sossel tries to run to freedom but is apprehended by the police. With the spy ring smashed, Lanyard's name is finally exonerated.