Sgt. Steve Johnson and his partner, Sgt. McManus, of the Los Angeles bunco squad, are assigned to investigate the possibility that all of the local charlatans are working for a single boss. While Steve and McManus question fortune-tellers, numerologists and tarot card readers, confidence man Anthony Wells ingratiates himself with wealthy widow Jessica Royce and her attractive secretary, Barbara Madison. After Tony learns that Jessica has been seeing Dr. Largo, a "consulting psychologist," he visits his former partner, crystal ball reader Liane Hill, and suggests that she plot with him to bilk Jessica. Liane, "graphologist" Annie Cobb and "swami" Drake, all of whom are known to Steve and McManus, join Tony and his cohort, Frederick Reed, to form the Rama Society. Tony declares Liane the group's leader and himself its silent partner, then instructs his workers to find out everything they can about Jessica's dead son Philip. After a number of anecdotes about Philip have been collected from various unsuspecting people associated with Jessica, Tony sends Reed to talk with Largo. Reed threatens to expose Largo, who he knows was once convicted of fraud under another name, unless he "advises" Jessica to visit the Rama Society. As instructed, Jessica attends a séance at the Society and is stunned to hear "Philip" talking to her, calling her by her pet name. Anxious to speak with Philip again, Jessica arranges for a private sitting the next day. Steve, meanwhile, learns that Liane, Annie and Drake have left their jobs and eventually tracks them to the Society building. After a fruitless discussion with Liane, Steve starts to leave and notices Jessica arriving for her sitting. Steve takes down Jessica's license plate number and, upon discovering her identity, goes to talk with her. To his surprise, Jessica dismisses Steve's warnings and remains firm in her support of the Society. While Steve and Jessica talk, Reed, who has followed Steve there, tampers with his brakes, causing Steve to crash as he is driving away from Jessica's house. With the sergeant momentarily out of the way, Tony orders the group to pressure Jessica to name the Society in her will as her sole beneficiary. A recuperated Steve, meanwhile, is told about Reed and Liane's past associations with Tony, and concludes that Tony is the ring leader. To trap Tony, Steve convinces his girl friend, aspiring movie actress Grace Bradshaw, to impersonate a medium and sends her to Dante, a retired magician, to be trained. Steve then travels to Kansas City to speak with Philip's best friend, Danny Bowman. Danny shows Steve the last letter Philip wrote to his mother before his wartime death, which Danny never mailed. Back in Los Angeles, after Liane convinces Jessica to change her will, a distressed Barbara tries to contact Steve. Unable to reach the sergeant, Barbara unwittingly confides in Tony her fears about the Society. Later, Barbara is killed when her car crashes, and Steve suspects murder. After Steve coerces Largo into advising Jessica to visit Grace, who is acting under the name Madame Bradshaw, Jessica is thrilled to learn about Philip's letter. Tony soon gets wind of Grace's operation and sends Drake to intimidate her. Instead, McManus and Dante beat up Drake, who rushes back to the Society and is followed by Steve. Before Steve can question them, Tony and Reed slip away and head for Dante's house. There they deduce that Grace is part of an undercover operation and take Jessica, who is having second thoughts about her will, at gunpoint, intending to kill her with another phony car accident. Steve, however, shoots Reed as he is fleeing Dante's and frees Jessica. Tony manages to jump into Jessica's car but, while being chased by Steve, loses control of the brakeless vehicle and crashes. With Tony's death, Steve is promoted to lieutenant and almost convinces Grace to marry him.