Once a thief, always a thief. This is the sorry lot of Eddie (Alain Delon), an ex-convict who tries his best to go straight. He marries Kristine (Ann-Margret), who bears him a child. Seeking out a new start in San Francisco, Eddie is dogged by vengeful cop Vito (Van Heflin), who thinks that the ex-con shot him years earlier. Eddie is arrested by Vito for a crime committed by someone else. Though he is set free, he is unable to find work after the truth about his past is revealed. Kristine is forced to take a job in a strip joint (her costumes are frustratingly modest) to make ends meet, a fact that sends Eddie spiralling into a depression-and, ultimately one last caper, engineered by his brother (Jack Palance). The grim proceedings in Once a Thief were originally put down on paper by novelist Zekial Marko, who plays a small role in the screen version.
~ Hal Erickson, All Movie Guide