Helen Brent (Claire Trevor) has just received a divorce in Reno, Nevada. That night, she goes to a casino and makes eye contact with a man who, though she does not know it then, is Sam Wilde (Lawrence Tierney), the other boyfriend of Laury Palmer (Isabel Jewell), who has been her neighbor during her stay in Nevada. Wilde, an insanely jealous man who won't abide anyone cutting in on him, spots Laury in the casino with her gentleman caller, Danny (Tony Barrett) and then lays in wait at her house to kill both of them. When Helen returns home, she finds Laury's dog loose outside and puts it back inside, discovering the bodies of Danny and Laury.