When New York City police officer O'Malley learns of a young man who is about to embark on a life of crime by taking part in a robbery, he takes the boy aside and tells him the story of Boomerang Bill, another wanna-be gangster who wanted to be a big shot in the New York crime scene. It seems that Bill fell for a pretty young dance-hall girl, and went up against local gang boss Tony the Wop when he insulted her. Tony, who never forgot a slight, found a way to make things very, very tough for Boomerang Bill, in a way that he never saw coming.

Just out of jail and vowing to go straight, former jewel thief Boston Blackie, undertakes the reformation of a pretty blonde who has stolen a necklace from a cabaret dancer. He learns that the jewel belongs to the mother of the blonde girl, and the blonde's philandering father gave it as a gift to the cabaret girl. Now, Blackie must find a way to return the necklace to the owner's safe without arousing the suspicions of the girl's family.

Blackie is implicated in a murder when he accidently sells a phony Charles Dickens first edition at an auction.