Stan Carlisle, an amoral carnival roustabout, exhibits a morbid fascination with the geek, a sideshow drunk who bites off the heads of live chickens in exchange for a daily bottle of liqour. Stan works with Zeena, a phony psychic who performs a mind reading act with her drunken husband Pete. Becoming intrigued when Molly, the naïve young assistant to Bruno the Strongman, tells him that Zeena and Pete were once vaudeville headliners who developed an elaborate word code worth its weight in gold, the handsome, highly manipulative Stan suggests that Zeena teach him the code so that they can work together. Zeena, who blames herself for her husband's dissipation, rejects Stan's proposal until he shrewdly suggests that their new act could fund the cost of Pete's cure. When Zeena consults her tarot cards for direction, however, they portend Pete's death, and alarmed, Zeena balks at making Stan her partner. Later that night, Stan buys a quart of liquor from the local moonshiner and stashes it in Zeena's trunk. When he encounters Pete shaking from alcohol withdrawal, Stan hands him the bottle, even though he knows that Zeena is determined to wean her husband from his addiction. The next morning, Pete is found dead from an overdose of wood alcohol and Stan realizes that he gave him the deadly drink by mistake. Weeks later, Stan has absorbed the code from the lonely Zeena, surpassing the abilities of his teacher. When a marshal comes to close down the carnival and arrest the troupe, Stan uses his charisma to play off the gullible lawman's fears, convincing him to drop the charges. After the marshal departs, an exhilarated Stan embraces Molly. When Molly protests that they are betraying Zeena, Stan claims his only interest in Zeena was in acquiring her code and then seduces the trusting girl. The rest of the carnival troupe has gathered at a seedy café, and when Molly and Stan arrive together, Bruno and Zeena realize that she has been seduced by Stan. After Bruno's threats force Stan into marrying Molly, Stan decides to leave the carnival and launch a new act with his wife. Some time later, Stan, now known as "The Great Stanton," is performing to great acclaim at an exclusive Chicago hotel. While attending the show one night, psychologist Lilith Ritter, suspicious of Stan's tactics, tries to outwit him by submitting a trick question about the health of her mother. After Stan replies that her mother is deceased, Lilith, impressed, invites Stan to her office. When their interview is interrupted by the unexpected arrival of Mrs. Peabody, one of Lilith's socialite patients, Stan leaves and Lilith proceeds to secretly record Mrs. Peabody's darkest confidences. Sneaking back into the office, Stan discovers the recording session and suggests using the information to bilk Lilith's wealthy clients. After denouncing Stan's proposal, Lilith throws him out. Later, following a performance, Zeena and Bruno visit Stan and Molly, much to Stan's displeasure. Upon consulting her tarot cards, Zeena foretells disaster if Stan strays from his present course and Stan, who believes in the cards though he pretends not to, angrily orders them to leave. Afterward, Stan is getting a massage when a whiff of alcohol triggers unpleasant memories of Pete's death. Panicking, Stan contacts Lilith and pours out his feelings of guilt to her. Despite Zeena's warning, Stan determines to embark upon what he terms "the spook racket." When Mrs. Peabody comes to the show to ask if she will ever see her daughter again, Stan, drawing on information he heard on Lilith's recording, responds that her daughter is dead and after accurately describing the departed girl, is about to relay a message when he faints. Controversy follows in the wake of Stan's disclosure, and when Mrs. Peabody informs her late husband's closest friend, the prominent Ezra Grindle, that she intends to help Stan bring spiritual comfort to others, the skeptical Grindle sets up a meeting with Stan to expose him. Swayed by Stan's charms and the promise of easy money, Lilith teams with Stan to convince Grindle of Stan's authenticity by feeding Stan the information from her secret recordings. Impressed by Stan's acumen, which he cloaks in religiosity, Grindle gives him $150,000 in cash to build a tabernacle and promises to buy him a radio station if he can establish contact with Dorrie, Grindle's long-lost love. After handing Lilith the cash for safekeeping, Stan studies photographs of Dorrie, then asks Molly to impersonate the dead woman's spirit. Declaring the ruse to be against God's will, Molly threatens to leave Stan who proclaims his enduring love, thus convincing the gullible Molly to pose as Dorrie. One evening, in a secluded area of Grindle's estate, Stan produces a distant illusion of Dorrie. When, entranced, Grindle begs Dorrie's forgiveness, Molly, unable to bear his anguish, approaches the distraught man, thus revealing who she really is, and runs off. Furious, Grindle attacks Stan, and after knocking down the elderly man, Stan speeds away with Molly and drops her off at their hotel with instructions to meet him later at the train station. After Stan informs Lilith about the debacle, she returns the cash-laden envelope and Stan hails a cab for the train station. En route, Stan opens the envelope and finds that Lilith has stuffed it with 150 one dollar bills, thus duping him out of a fortune. After Stan returns to confront Lilith, she cunningly tries to convince him that he is mentally imbalanced and reminds him that she possesses a recording of his confession about his complicity in Pete's death. When Stan hears a police siren approaching in the distance, Lilith insists that he is hallucinating and offers to commit him. Realizing that he has finally met his match, Stan runs away to meet Molly. Upon arriving at the train station, a distraught Stan hands Molly their life savings, exhorts her to find her way back to the carnival, then kisses her as her train pulls away. As headlines trumpet his fall from grace, Stan holes up in a cheap hotel room and begins his descent into alcoholic oblivion. Reduced to telling fortunes to hoboes along the railroad tracks, one day Stan comes across a carnival and asks for a job as a palm reader. Instead, the carnival owner offers him a drink and the job of geek. As recognition slowly dawns on Stan, he smiles and replies he was "made for it." Later that night, word spreads that the newly hired geek has gone berserk. Alarmed, Molly, who uknown to Stan, works at the carnival, goes to investigate and to her horror, finds Stan raving in the carnival yard. Running to Stan, Molly assures him that she will look after him, and in his alcoholic haze, he gratefully embraces her.