A man tries to save his fickle ex-wife from her criminal lover.

In the parking lot of the Round-Up bar in Los Angeles, Steve Thompson meets secretly with his married lover, Anna Dundee, and reassures her that their plan to run away together will not fail. Steve then fights with Anna's gangster husband Slim inside the bar, but police lieutenant Pete Ramirez, Steve's old friend, breaks it up. Steve refuses to press charges against Slim, who is supposedly leaving for Detroit the next day, and Pete, disgusted by Steve's destructive behavior, leaves. Unknown to Pete, Steve, Slim and his gang are plotting to rob an armored truck, which will be driven by Steve, who works for an armored car company, and staged the fight to fool Pete. The next morning, as Steve and Pop, a co-worker and family friend, leave on their scheduled payroll run, Steve recalls the events that led him to commit robbery: Eight months before, Steve returns to his home in Los Angeles after two years of drifting. Although he fights the urge to see Anna, to whom he had been briefly married, he starts dropping by the Round-Up, the bar they used to frequent together. Eventually, he and Anna reunite, and she chastises him for not contacting her sooner. Passion between the combative couple quickly reignites, and they begin seeing each other again. Steve's renewed romance distresses both his mother and Pete, who distrust the manipulative Anna. Pete is particularly concerned because he knows that Slim is also after Anna. Then one night, Steve learns that Anna has gone to Yuma to marry Slim. Although embittered, Steve cannot resist Anna when he later runs into her at Union Station. Slim has gone to Las Vegas, and Anna meets secretly with Steve, complaining that she is miserable. Anna shows Steve bruises on her back inflicted by the controlling, brutal Slim and tells Steve that she married Slim, who had been pursuing her since their divorce, only because Pete had threatened to send her to prison if she continued to see Steve. Later, a drunken Steve confronts Pete, who admits he threatened Anna, but warns his friend about crossing Slim. Steve continues to see Anna, but one day, she comes by his house and informs him that Slim has found out about their affair. At that moment, Steve discovers Slim and his thugs in his living room. Thinking fast, Steve tells Slim that he summoned Anna to his house in order to discuss his plan for an armored car robbery. After Steve convinces Slim that they can pull off the payroll heist, the first of its kind in many years, because he will be their "inside man," Slim gathers his men together and carefully plots every detail of the robbery. Part of the plan is to broadcast that Slim is leaving for Detroit on the same day as the proposed robbery and throw a going-away party at the Round-Up the night before. Back in the present, Steve drives his truck to the appointed spot, where Slim and his men fire tear gas at Steve and Pop. Pop then begins shooting at the robbers, who return fire, fatally wounding him. Enraged because Slim had agreed not to harm Pop, Steve shoots Slim and is himself badly wounded. Slim and his gang flee with the money before the police arrive, and Steve wakes up later in a hospital. Although Steve's family and the public believe that he is a hero, Pete has deduced Steve's involvement and warns him that Slim will be after him if Anna has disappeared. Panicked, Steve, who had arranged for Anna to meet him in a Palos Verdes cottage, asks Nelson, a man he believes is visiting his sick wife, to watch the door for him during the night. The next morning, Nelson reveals that he is Slim's hired killer and drags Steve from the hospital. As they are driving to see Slim, Steve bribes Nelson into taking him to Anna. As soon as Steve pays Nelson off, a terrified Anna starts to pack, telling Steve that he is not strong enough to go with her, and she is not tough enough to stand by him. Before she can escape, however, Slim, having anticipated that Steve would bribe Nelson, bursts in. As police cars close in, Slim shoots the couple dead.