Ventriloquist/hypnotist The Great Vorelli has an amazing dummy named Hugo that can apparently walk and talk without Vorelli operating him. Vorelli's act with the dummy is intense, complete with harsh insults and threats. After Vorelli meets beautiful heiress Marianne Horne, he hypnotizes her, causing her to suffer from a severe fever that spirals into a coma. Marianne’s boyfriend Mark, a newspaper reporter (William Sylvester), is suspicious and starts investigating Vorelli’s past. He discovers that a man named Hugo was killed several years earlier during one of Vorelli’s shows in Berlin. Apparently Vorelli stole Hugo’s human soul and transferred it into the body of the dummy. Marianne awakens from her coma, and announces she will marry Vorelli. The triumphant hypnotist brags to Hugo about his plans for Marianne and his plot to transfer her soul into a female dummy. A violent confrontation between Hugo and Vorelli results in a chilling climactic switch.