An embittered Louie Peronni returns from prison to find that his sister, Juli Peronni, is engaged to policeman Eddie Farrell, and also finds that his secret wife Annie Qualen has placed their baby girl in a foundling home. With his old gang again, Louie plans a robbery of a fur warehouse. Louie shoots down the night watchman and is trailed home where his father Guiseppe Peronni persuades him not to fight it out with the police. Determined to let Louie take the full rap, the gang kidnaps the district attorney's daughter.

In Puerto Rico to investigate a glut of contraband diamonds that are flooding the world's jewel market, Mr. Moto and his sidekick, a wrestler, find themselves involved in murders by thrown daggers, the frame-up of an overstressed Army colonel, and a pirate gang led by an unknown boss who has inside knowledge of the ensuing investigation.