Johnny Allegro (played by George Raft) is a small-time florist who is approached by Treasury Department officials to help them catch a notorious criminal named Morgan Vallin (played by Luther Adler), also known as "The Duke." Johnny agrees to help, in exchange for a clean slate and a fresh start.
As he infiltrates the criminal underworld, Johnny befriends a lounge singer named Glenda Chapman (played by Nina Foch) and begins to fall for her. However, he also catches the attention of Vallin’s henchman, Rico (played by Eduardo Ciannelli), who becomes suspicious of Johnny's intentions.
As Johnny gets closer to Vallin, he realizes that he has been duped by the Treasury officials - they are using him as bait to catch Vallin, and they have no intention of helping him start a new life. With his life in danger and his dreams shattered, Johnny must find a way to outsmart both Vallin and the Treasury officials before it’s too late.
The film is a classic film noir, featuring tense action, dramatic performances, and moody cinematography. Raft gives a strong performance as the titular Johnny Allegro, while Adler is suitably menacing as Vallin. Foch is also memorable as the conflicted lounge singer caught between two dangerous men.