The ambitious Stanton “Stan” Carlisle works in a sideshow as carny and assistant of the mentalist Zeena Krumbein, who is married with the alcoholic Pete. The couple had developed a secret code to pretend to read minds and was successful in the show business before Pete starts drinking. Stan stays with them expecting to learn their code and leave the carnival to be a successful mentalist. Stan also flirts with the gorgeous Molly that lives in the carnival with the strong Bruno. Zeena and The Savage, an alcoholic man that eats live chickens that the audiences believe that is a savage, are the greatest attractions of the sideshow. When Stan gives booze to Pete and he dies, Stan finds that Pete had drunk methyl alcohol and not his booze, but he feels guilty for the death of him. Zeena teaches the code to him and Molly helps Stan to learn them. After an incident, Stan is forced to marry Molly and he decides to move to Chicago with her to become a sensation in a night club. One day, he meets the psychologist Lilith Ritter and he finds that she tapes the sessions with her clients from the high-society. The trickster Stan envisions a scheme to raise a high amount of money swindling rich people. But his ambition brings him back to the life in the sideshow.
Stanton Carlisle (Tyrone Power) raised in an orphanage and reform school is a drifter who works as a barker in a carnival. He is fascinated by the Geek side show in which a crazy man performs by biting heads off of live chickens and is paid off with a bottle of rotgut and a cot to sleep. Charming and good-looking, Stanton spends much of his time casually romancing Zeena (Joan Blondell) the second half of a mentalist act she works with her husband, alcoholic Pete (Ian Keith). Most of Stantons other affections are directed toward Molly (Coleen Gray) whose boyfriend Bruno (Mike Mazurki) jealously tries to interrupt whenever Stanton is nearby. When Stanton learns of a former mind-reading act that Zeena and Pete had before they joined the carnival he approaches them with the idea of reviving it but is rebuffed with the excuse from Zeena that the couple are saving the act to sell as money for their retirement, and also Pete is too drunk to perform it. One night Stanton accidentally gives Pete wood alcohol to drink killing the older man leaving the younger man with a lingering sense of guilt. Needing to find a new act Stanton convinces Zeena to start up the old act and they do so at great success. Stanton and Molly fall in love and are reviled by Bruno and Zeena and kicked out of the Carnival so Stanton takes the mind-reading act on the road with Molly with even greater success than before. Once in the limelight Stanton realizes something that Pete had told him years earlier that the audience wants to be duped because it gives them a sense of hope, and this small truth empowers Stanton to develop his performance skills to even greater heights. With the aid of a beautiful society psychiatrist Dr. Lilith Ritter (Helen Walker) Stanton starts up an act in which he channels the dead relatives of high-class socialites. When one of his scams backfires Stanton finds that his alliances have fled so he sends Molly away to the carnival and he leaves alone, soon becoming a hobo with many other forgotten men and then an anonymous bum, who wanders into a carnival taking the only job offered him, that of a Geek, which he gladly accepts.