Helen Ferguson, Barbara Stanwyck, sits with her baby as Bill Harkness, John Lund, reads a book and tries to stay calm while the phone rings and police tell them they’re on the way to their home.
A year earlier in New York, Helen is eight months pregnant, unmarried, and broke. She turns to her unfaithful boyfriend Stephen Morley, Lyle Bettger, who refuses to help but slips under the door an envelope containing a five-dollar bill and a one-way train ticket to San Francisco. Retrieving the envelope, Helen spills the money and realizes she has no choice but to board the train. Her journey ends in tragedy when the train crashes; authorities pull her from the wreckage and mistake her for Patrice Harkness, the real mother who was killed in the crash. Helen gives birth to her baby in the hospital and, as the family of the dead husband, Hugh Harkness, Richard Denning, welcomes her into their home, believing she is Patrice. The Harkness clan, spearheaded by the head of the family, Mr. Harkness, Henry O'Neill, offers her a chance at a new life, and their generosity shades into a protective, almost possessive regard. Helen’s quiet deception grows into a fragile semblance of normalcy, and Bill Harkness begins to fall in love with her, complicating loyalties and long-buried secrets.
Stephen Morley tracks Helen down after the wreck, and instead of unmasking the truth, he demands money and pushes Helen toward a marriage she does not want. He tries to leverage the situation by threatening exposure, forcing Helen to confront the danger he represents. In a desperate turn, Helen obtains a gun, goes to Stephen’s office, and finds him dead on his bed but fires the weapon anyway. Bill arrives to help dispose of the body and erase evidence, while his mother, Mrs. Harkness, Jane Cowl, plays a crucial but uneasy role in keeping the family’s secret intact.
Bill’s mother dies of heart failure, but not before she writes a letter to Helen, entrusted to their maid, promising to deliver it only if the police come for Helen. In the letter, Mrs. Harkness claims to have killed Stephen, a claim that she could not have fulfilled. Three months later, police reopen the case, finding Stephen’s body and the conspicuous check Helen had given him. They come for Helen, who eventually confesses to shooting Stephen, only to learn that her bullet missed him and another caliber bullet was found in his body, while Stephen’s girlfriend comes forward to corroborate the shooting. With the truth unfolding, Helen and Bill confront the consequences of their choices, and in a moment of relief and reconciliation, they embrace, facing an uncertain but hopeful future together.
