When hard-boiled Hollywood Detective Sergeant "Stake-Out" Kelly and his partner John Connors prevent the robbery of a gas station, they win praise from the police force but gain the antipathy of the city's criminal element. While the underworld plans to kill Kelly, he is promoted to lieutenant and ordered to capture a gang of jewel thieves who have been robbing women in public places. As Kelly stakes out one such place, a drive-in sandwich stand, he is warned by Mary Higgins, one of the attendants, that he is being followed. Kelly soon becomes smitten with Mary, who tells him that she came to Hollywood from Iowa hoping to become a movie star. Their romance flourishes until Kelly accuses Mary of being in league with the gang and tipping them off about a prisoner who was being tranported by the police. To prove her innocence, Mary goes undercover for the police and takes a job at the gang's cafe so that she can inform on them. Mary's plan goes awry, however, when the gangsters find her hiding in the cafe while they are planning a robbery. Mary is forced to accompany the gangsters on the robbery, but she is freed when the gang is surprised by the police. After the gang's capture, Kelly sends Mary back to Iowa, but then changes his mind and wires her on the train, telling her that he is coming after her.