During a performance of his popular radio show, Alex Gregor, better known as "Gregor the Great," places his fiancée, Maura Daniel, into a telepathic state under hypnosis. A drunken skeptic in the audience accuses Alex of being a fake, so the angry mentalist begins to hypnotize him, only to have the man drop dead. Although medical examiners state that the alcoholic died of a heart attack, a guilt-ridden Alex proclaims himself a murderer and breaks his engagement. In order to shield the mentalist from adverse publicity, George Keene, Alex's business manager, arranges for his client to go to work for his old friend, Mme. Valerie Monet, as a lecturer at her wax museum. While both Valerie and Nina Coudreau, her niece, are thrilled to have Alex in their museum, Rudi Poldan, a mentally disturbed plastic surgeon who works at the museum as a sculptor, becomes jealous of their attentions toward Alex. Jealousy rears its ugly head when Valerie falsely accuses Alex of romancing her niece. During their ensuing argument, Valerie faints and Alex leaves the museum. Returning the next day with George, Alex learns that Valerie has disappeared and Police Inspector Brant suspects him of her murder. Unknown to all, Rudi has hidden the comatose Valerie among his wax statues. When Nina discovers her aunt, she rushes to Alex's room, and accuses him of plotting against Valerie with the mad surgeon. Unknown to Nina and Alex, Rudi has been conspiring with George to have Alex committed and gain control of his estate. Later, the two meet at the wax museum, where Rudi shows George how he has placed both Valerie and Nina in states of suspended animation. Upon closer examination, however, they discover that Valerie is dead. Now guilty of murder, George insists that they get rid of both women, even though Nina is still alive. Meanwhile, Alex has gone to Maura's apartment to ask for her help, and the two arrive at the wax museum to find a disheveled George. Alex then places Maura into a psychic trance, during which she exposes both George and Rudi. George attempts to escape, only to be captured by an eavesdropping Brant. Alex and Maura then rush down to the furnace room to save Nina. Startled by their appearance, Rudi falls into the furnace and dies. Later, as newlyweds Alex and Maura are about to head off for their honeymoon with their new ward, Nina, Brant arrives and asks for Alex's help in solving a case. Alex replies, "Oh, Inspector, I thought you knew. It's all done with mirrors."