Once a Thief is a 1950 American crime film noir directed by W. Lee Wilder starring Cesar Romero, June Havoc, Marie McDonald and Lon Chaney Jr.^[1]

Margie Moore, a miserable San Francisco woman, turns in desperation to jewel robbery. She narrowly escapes apprehension in a heist and moves to Los Angeles, where she takes an honest job as a waitress. Her troubles resume when she falls in love with smooth-talking Mitch Foster, who reveals his true colors by stealing all of her money and then informing the authorities about her.

In prison with her partner-in-crime Pearl, Margie is visited by Mitch and waitress friend Flo. Mitch continues to try to extract money from her. Margie overpowers a doctor and slips away from prison disguised in the doctor's clothes. Law-enforcement authorities look for her at Mitch's and discover his illegal activities there. Mitch tries to escape, but Margie lures him to a deserted spot and shoots him.

• Cesar Romero as Mitch Moore
• June Havoc as Margie Foster
• Marie McDonald as Flo
• Lon Chaney Jr. as Gus
• Iris Adrian as Pearl
• Jack Daly as Eddie
• Marta Mitrovich as Nickie
• Ann Tyrrell as Dr. Borden
• Michael Mark as Milton
• Kathleen Freeman as Phoebe
• Dana Broccoli as Jane (as Dana Wilson)
• Bill Baldwin as Bondsman
• Frances Blumfeld as Lt. Francis Blumfeld (as Lieutenant Frances Blumfeld)
• Gwendolph Dusuau as Deputy Gwendolph Dusuau (as Deputy Gwendolph Dusuau)
• John P. Battema as Chaplain John P. Battema (as Chaplain John P. Battema)
• Dorris Mack as Deputy Dorris Mack (as Deputy Dorris Mack)
• Irma Kunow as Deputy Irma Kunow (as Deputy Irma Kunow)
• Lloyd C. Smith as Officer Lloyd C. Smith (as Officer Lloyd C. Smith)
• Ruth Moore as Police Sergeant Ruth Moore (as Sergeant Ruth Moore)
• Leauta Larsen as Deputy Leauta Larsen (as Deputy Leauta Larsen)