The movie begins with 19 year-old Marie Allen (Eleanor Parker), being delivered to the Women's State Prison. Although she was convicted of armed robbery, the reality is that her husband was the real culprit. She just happened to be with him when he commited the robbery, and after he was killed in the hold-up, Marie was arrested and sent to prison for a period of 1-15 years. Upon admission to the prison, it is discovered that Marie is two months pregnant.
Though prison superintendent Ruth Benton (Agnes Moorehead) is warm and caring and really wants to make life easy for her pregnant first-time offender, Matron Harper (Hope Emerson) has other ideas for the women under her charge. Harper is coarse and hardened and takes bribes from her charges. Without payment from them, she makes life difficult indeed, and since Marie has no wherewithall to pay a bribe, she is soon a target for the matron's brutality. Though Marie longs to be a well-behaved inmate and earn parole in ten months, being in with hardened criminals cannot help but affect her...and not for the good.