Fed up with the raising crime in Miami, the police chief and the leading members of the city council hire a former Miami gangster, gone straight, to help eliminate the biggest crime syndicate in the city.

Chuck Wheeler gets out of the Pen and sets up an elaborate heist of Vegas casino money travelling by armored truck. He enlists the help of shady club owner Joe Darren and his ex-cellmate's wife, Vi. Vi's husband Mike is a trigger happy and jealous hothead and will not grant her a divorce. Mike escapes from prison right before the armored truck job goes into motion and promises trouble as he tries to locate his associates and his wandering wife.

Mark Fallon, with partner Kansas John Polly, tries to introduce honest gambling on the riverboats. His first success makes enemies of the crooked gamblers and of fair Angelique Dureau, whose necklace he won. Later in New Orleans, Mark befriends Angelique's father, but she still affects to despise him as his gambling career brings him wealth. Duelling, tragedy, and romantic complications follow.

Accused of killing a woman on a train, Sharon Carlin runs home to find another corpse there too!

After several years of supporting parts, Victor McLaglen once more landed a leading role in Republic's City of Shadows. McLaglen plays Big Tim Channing, an ageing but powerful gangster who raises young newsboy Dan Mason as his own son. Upon reaching adulthood, Mason (John Baer) becomes a law student, with the covert (and illegal) help of Channing. Despite his checkered past, Mason opts for honesty when he falls in love with Fern Fellows (Kathleen Crowley). This decision ultimately spells the doom for Mason's mentor Big Tim.