Former New York City mobster Gloves Donahue, now a professional gambler, will eat only cheesecake baked by his mother's neighbor, Mr. Miller. When Miller is murdered, Gloves is urged by his mother, to whom he always listens, to investigate, and although he is reluctant at first, his interest is piqued when an attractive young woman comes looking for Miller and disappears as soon as she learns he is dead. That night, nightclub owner Marty Callahan telephones Gloves to demand that he retrieve Mrs. Donahue, who has discovered Leda Hamilton, the mysterious woman from that morning, singing at Callahan's club. When Gloves questions Leda, she provides simple explanations for each of his questions, and before long, she is dragged away by her sinister accompanist Pepi. Curious when a man runs outside and speeds away in a taxi, Gloves rushes inside just in time to see fatally wounded Joe Denning, one of Callahan's men, stagger from a dressing room. Before he dies, Denning tells Gloves that Leda has been kidnapped. Through his contacts, Gloves, who is mistakenly accused of Denning's murder, traces the taxi to a warehouse. Leaving his driver Barney behind, Gloves and Sunshine, one of his cronies, sneak inside. While Gloves looks around, Sunshine is knocked out and carried away, and when Gloves tries to find him, he is driven away by gunshots. Gloves suspects that the warehouse is connected to an exclusive auction house around the corner, where an auction is being conducted. Gloves bids on a piece in order to take a look at the offices, but once inside, he is spotted by Pepi and Leda, who knocks him unconscious. Gloves awakens in the warehouse, tied up next to the missing Sunshine. To Gloves's surprise, Leda helps free them from their bonds, and later, Gloves and Sunshine overpower their captors. Inside the auction house, the pair find evidence that the mysterious group consists of German spies and fifth columnists, as well as a notebook that indicates that Leda's father has died in Dachau. When Gloves tries to take Hall Ebbing, the leader of the spies, to the police, however, Ebbing summons the others, and Gloves barely escapes with an unconscious Leda during the ensuing gunfight. While they run from the Germans, Leda explains that Miller was forced to work for them against his will. She also reveals that she must work for them or they will kill her father, but when Gloves tells her that her father is dead, she readily agrees to help him. The police do not believe Leda's testimony, however, and Gloves is forced to call on Callahan for help in avenging Denning's death. Gloves and Sunshine infiltrate a meeting, where they learn that the Germans plan to blow up a ship docked in the Brooklyn shipyard. They keep the group distracted long enough for Callahan's men to arrive. Ebbing escapes, determined to blow up the ship by himself, and Gloves follows him. At gunpoint, Ebbing forces Gloves to drive a small boat toward the ship, but at the last minute, Gloves turns the boat sharply and knocks Ebbing overboard. Gloves is declared a hero and charges against him and Leda are dropped.