French artist Paul Panois is being held captive in America by a gang of Nazi sympathizers who are forcing him to create counterfeit U.S. war tax stamps. When Panois learns that his daughter Marianne, whom the group was holding hostage in Paris, has escaped on an ocean liner bound for America, he also escapes and notifies the district attorney's office that he will give them valuable information if they ensure his daughter's safety. District Attorney Winton sends his assistant, P. Cadwallader Jones, who is known as Jonesy, to meet Marianne when her boat lands. Panois has sent Marianne a claim check for a trunk containing the counterfeiting plates, but when Jonesy and Marianne try to claim it, they discover that the station attendant, Oscar Mayberry, has sent it to be auctioned by the Women's Defense Corps because it was not claimed within thirty days. Jonesy and Marianne attend the auction, but upon opening the trunk, discover Panois' body instead of the plates. Jonesy's problems are complicated by his reporter girl friend, Terry Parker, who is not only jealous of his attentions to Marianne but upset because he did not give her the scoop on the Panois murder. Jonesy, who is promoted to district attorney after Winton joins the FBI, tries to keep Oscar away from Terry so that she does not reveal his identity, as Oscar can identify Joe Martin, one of the gang. His efforts fail, however, and Terry's snooping inadvertantly leads Joe to Oscar, who is then killed. Terry suspects Mrs. Perkins, the leader of the Women's Defense Corps, of being involved in the gang, and while she questions her, she is shot at by Maxie Schmidt, another member of the gang. Maxie is killed by Dave Cleary, one of Jonesy's investigators, and is implicated in Panois' death. Suspicious now of couturier Maurice Vaughn, who is friends with Mrs. Perkins, Terry gets Marianne a job in his shop to spy on him. Marianne recognizes Joe from Oscar's description of him and realizes that Vaughn is the secret leader of the gang. Vaughn knocks her out, and after wrapping her in bandages, puts her in the display window until he can take her away after the shop closes. When Terry comes by to see Marianne, she takes a picture of the window, and after Marianne is declared missing, Terry recognizes her in the picture despite the bandages obscuring her face. With the aid of Mrs. Perkins and her corps, Terry traces Vaughn to the dairy where Panois was being held, and where Marianne is now held. Terry is captured by Vaughn, who explains that counterfeiting the war stamps is part of a campaign to disillusion Americans and make them mistrust their government. A series of clues leads Jonesy to the dairy, and while he and Joe fight, the women round up the rest of the gang. Jonesy frees Terry and Marianne before they are crushed by a load of grain in a silo, then reconciles with Terry on the ride back to town.