Mal Granger (O'Brien), boss of a rising California bookie organization, is forced to make a 50-50 deal with the Eastern syndicate leaders, Carl Stephans (Kruger) and Larry Mason (Porter). When he learns that Mason is shortchanging him, Mal goes berserk. He arranges for Larry's murder and then slays the hired killer when the latter tires to blackmail him. Mal then flees with Mason's wife Gail (Dru), with whom he has fallen in love. Both the syndicate mobsters and the police close in. Mal and Gail are trapped by the police in Boulder Dam. There, after a desperate chase through a labyrinth of tunnels, generators and stairs, Gail is captured and Mal is shot down by police bullets.