Charles Hale, a journalist, is working in Brighton distributing cards and prizes as part of a game organized by his newspaper when he realizes that a mob there is trying to murder him. Hoping that he will be safe if he is with someone else, he attaches himself to Ida Arnold, an affable middle-aged entertainer who becomes fond of the man, and who, nevertheless, is killed by the seventeen-year-old gangster Pinkie Brown. Pinkie killed Hale in revenge for Hale's involvement in the death of Kite, the former leader of Pinkie's gang and a father figure to him.
Due to a poorly considered move by Spicer, a member of Pinkie's gang, Pinkie fears that their alibi may be compromised. In order to take care of matters, he warns Rose—the young, innocent, and highly observant restaurant waitress who saw Spicer—to forget about what she has seen. He takes her out on a date to try to convince her further.
To deal with Spicer, Pinkie takes him to a horse race, where both Spicer and Pinkie are nearly knifed to death by henchmen of Colleoni, a rival gangster. Finding that Spicer has not been finished off, Pinkie pushes him off a stairwell to his death.
As Pinkie gains the affection and loyalty of Rose through dates with her, Ida begins an amateur investigation into Hale's death and becomes fixated on Rose, who she is sure knows something about Hale's murder.
Fearing that he cannot keep Rose from suspecting him, Pinkie decides to marry her to silence her, since a wife is not allowed to testify against her husband. He also loses his virginity to her, thus getting over his revulsion against sex. However, he becomes horrified by the idea that she could become pregnant, bear his child, and then settle into a family life with him. Determined to avoid this fate, he tries to coax her into killing herself by the false suggestion of a double suicide.
At the last moment, Ida, along with a policeman and a member of Pinkie's gang, finds the young couple and save Rose. When the acid Pinkie tries to throw backfires on him, he stumbles off a cliff to his death.
