Betty Miller (Norma Moore), a young, naive woman who has recently moved from the country to Los Angeles with her mother, is seduced by grifter Don Bigelow (Robert Vaughn). Don tricks Betty into helping him rob a theater, but the two are caught by police, leaving Don in jail and Betty alone, on probation, and pregnant.
Unwed Mother contains examples of:
- Back-Alley Doctor: Gertie (Billie Bird), a stripper Betty met during her short time in jail, directs her to a creepy, drunken abortionist (Timothy Carey). Betty can't bring herself to go through with the procedure and flees his office. Later, she hears he was arrested after one of his patients died.
- Does He Have a Brother?: When Don brags about Betty to his friends, exaggerating how well-off she is, one of them asks, "Does she have a sister?"
- Fainting: Early in her pregnancy, Betty faints. Her mother finds her and calls a doctor, which is how they find out that Betty is pregnant.
- Good Girls Avoid Abortion: Betty's reason for not getting an abortion is "It's not mine to kill."
- Replacement Goldfish: A couple decides to adopt Betty's son because they feel lonely after the death of their own son Joey in World War II.
- Shotgun Wedding: Narrowly averted. Don learns that he'll be let out of prison and put on probation if he marries Betty, and eagerly accepts. However, Betty quickly realizes that Don never really loved her and rejects him, and he's sent back to prison.
