A wealthy Philadelphia man's fortune is left to Sister Sara, the leader of a spiritualist group, along with a jeweled necklace that accompanies the bequest. The setup seeds a tense, city-spanning heist as the story folds between luxury estates and the grittier corners of mid-century urban life. To steal the jewels, Nat Harbin forms a small gang that includes Baylock, Dohmer, and Gladden, the daughter of his mentor. Gladden is dispatched to case the estate, posing as a devoted follower of the group’s work, and she deftly uncovers where Sister Sara’s safe is kept.
During the robbery, Harbin parks near the mansion while his two partners hide nearby. Harbin tells the policemen that he’s had car trouble and is waiting for help in the morning, a gambit that lets him slip the theft past attention. He then enters through a window, cracks the safe, and makes off with the necklace. The thieves change their license plates and race away, but they’re baited by another car that trails them. A routine pursuit becomes a shadowy game of nerves and misdirection.
Back at the hideout, Baylock and Dohmer are eager to fence the necklace and claim their share, yet Harbin counsels patience, arguing they should wait for distractions in the news to maximize what a fence might fetch. An officer who spoke with Harbin later helps create an artist’s sketch of the suspected robber, layering the case with pressure and looming risk. As the tension thickens, Harbin reveals to Baylock the truth about his and Gladden’s past, laying bare the intimate and dangerous entanglements that fuel the scheme.
An altercation with Dohmer, who lusts after Gladden, pushes Harbin to send Gladden off to Atlantic City to wait for him. Gladden takes the train, and in Atlantic City she’s followed by a man who soon forms a cautious, growing bond with her. Across town in Philadelphia, Harbin meets Della, a woman who invites him into her apartment. He falls asleep, but when he wakes, she’s gone—and outside he spots her with the same man who’s been following Gladden, overhearing their plans about the necklace.
Realizing Gladden is in danger, Harbin speeds toward Atlantic City with Baylock and Dohmer, only to be flagged by a toll booth operator who recognizes him from the sketch and alerts authorities. The gang’s car is halted for a routine traffic stop; panic erupts and Dohmer shoots the officer, who fires back and kills him. Harbin and Baylock abandon the car with Dohmer’s body near Atlantic City, seeking refuge in a deserted shack. Harbin learns that the man who trailed Della is the same person pretending to be Gladden’s boyfriend, and he orchestrates a risky plan to secure his own escape.
A crucial move unfolds when Harbin calls Della to coordinate with Gladden’s room. He eventually discovers that the jewels are hidden in Gladden’s room, while Gladden herself stashes the jewels in her musical jewel box after the quarrel with Harbin. Charlie, one of the officers who questioned Harbin, arrives in Atlantic City and becomes a volatile wildcard in the confrontation.
Inside the shack, Charlie kills Baylock and offers to spare Harbin and share the money if Harbin yields the necklace. Della arrives, and Harbin reveals the location of the jewels in Gladden’s room, prompting Charlie to head out. Della holds a gun on Harbin as he contacts Gladden to arrange a meeting. The trio eventually converges at Atlantic City’s Steel Pier, retreating to a distant attraction to dodge Charlie, who tracks them down when Gladden accidentally drops the music box and it plays its tune.
They sit together at a show, and Harbin makes a desperate offer: the necklace in exchange for Gladden’s life. As Gladden leaves, Charlie shoots Harbin, and the police arrive, congratulating Charlie on solving the case. Charlie claims Harbin threw the jewels into the ocean, but Della’s arrival reveals the truth that he’s cutting her out of the deal. When Charlie lunges at Della, the head detective steps in, punches him, and finds the jewelry in Charlie’s pocket. Charlie is handcuffed and led away, bringing the dangerous chain of deceit to a close.
