Aided by two accomplices and his buxom half-sister and small-time crook, Gladden (Jayne Mansfield), burglar Nat Harbin (Dan Duryea) steals a valuable diamond necklace from the mansion of a noted spiritualist. Having already been tipped to the plan, an unscrupulous cop named Charlie tails the thieves to Atlantic City where, after killing two of Nat's henchmen, he kidnaps Gladden and demands the necklace in exchange for her safe return. However, even when he relents and hands over the loot in order to guarantee Gladden's safety, Nat learns that Charlie won't be satisfied until he is out of the way, too.