The movie opens in a darkened room. An attractive young woman, Miss Thompson (Evan MacNeil) walks in carrying a bottle in her right hand and towel in the other. She turns on the light and we see it is the kitchen. She pours some of the white creamy liquid from the bottle into her hand, then lathers her hair. She turns on the stove and we see the flame from below the burner grate. Her hair catches fire and she screams. Title and credits roll.
The woman's head is now bandaged and she is on a gurney, still in her kitchen. The Emergency Doctor (Jimmy Lydon) finishes some notes as the ambulance attendants prepare to move Miss Thompson to the hospital. Det. Sgt. Dave Kennedy (Joe Patridge) arrives on scene and removes the gawking neighbors from the kitchen doorway. He confers with the doctor and discovers, "Another self-inflicted mutilation, the stove." Dave tries to question the woman, but she just rambles then dies of shock. The count is now eleven women who have mutilated themselves.
At police headquarters, Dave Kennedy reviews the grisly clues in some of the mutilations: a desktop fan, a coffee cup, and a straight razor. He decides to confer with Dr. Phillip Hecht, the police psychiatrist. Phil has to write a paper for the Journal of Criminal Psychiatry and is trying to find a topic. Dave is stumped by the cases and discusses the latest. Dave tells Phil he has a date with his girlfriend later and she wants to see a hypnotist show. Phil hates the idea of hypnotism, a legitimate medical tool being used for amusement and entertainment, "They prostitute the entire science of hypnosis."
Desmond (Jacques Bergerac), dressed in formal wear, white tie and tails, is on stage with four men sitting in chairs. The subjects are under hypnosis and are given various commands: one man can't open his eyes, another told he is hot, a third is told he is cold, and the last man is told he is a mean dog. Dave is in the audience with his girlfriend, Marcia Blaine (Marcia Henderson). Sitting next to her is Marcia's friend, Dodie Wilson (Merry Anders). Dodie is impressed by Desmond's act, but Dave voices his skepticism. For the final act, Desmond calls for three female volunteers. Justine (Allison Hayes) joins Desmond on stage for the final act. She nods her approval of the women chosen. Dodie volunteers to be the third woman selected. The last demo is the defiance of the law of gravity. Desmond hypnotizes Dodie, then pushes her back into the arms of one of the volunteers. Dodie is floating when Desmond whispers something into her ear while Justine observes just off stage. Before Dodie is awakened, Desmond tells her, "Now when you awake, you will not remember anything that has happened to you on this stage...You will remember only the order I gave you." As Dave, Marcia and Dodie exit the theater, Dodie tells her friends she remembers nothing. Upon seeing the theatrical poster of Desmond, Dodie's mood changes and she grows cold and distant. She makes an excuse to go home and pretends to take a cab home, but actually goes back to see Desmond. Dodie is now at home preparing for bed. She fills the bathroom sink with water and pours liquid into the sink. After she pours most of the bottle into the sink we see it is a bottle of concentrated sulphuric acid. She proceeds to wash her face, then looks up at herself in the mirror. Her face is scarred and gray. She faints, knocking the bottle of acid on the floor.
The Los Angeles Chronicle newspaper headline reads, "12th Mutilation Victim," and "Acid-Burned Beauty Found Unconscious." A doctor (Fred Demara) is spraying a paraffin based solution on Dodie's back. Dave and Marcia come to visit her in the hospital. Before she will allow her friends in to see her she asks the doctor to turn the light away. Dodie pleads, "Dave, what happened? Tell me what happened last night." She tries her best to remember, but is unable to account for the acid. Dave and Marcia leave the hospital. Dave tells Marcia all the victims, including Dodie, tell the same story. Marcia suspects the only clue worth investigating is the hypnosis angle. Dave gets an emergency call on the car radio and departs. He leaves Marcia off at the hypnotist theater at her suggestion. They agree to meet at her apartment later that evening. Marcia volunteers for the three woman anti-gravity act. Desmond hypnotizes her. Desmond uses a flashing "eye"--a strobe light. At Phil's apartment, Marcia tells Dave, "He did it, I'm sure he did it." She recounts the details of the show with Dave and Phil, including a detailed description of the "eye" prop. The final detail she discloses is that Desmond's whispered command was to return to the theater at midnight for a date. The three drive to the theater and Marcia goes back to see Desmond. Marcia waits in Desmond's dressing room. While there, she discovers the box with the "eye" and opens it. As it strobes, Desmond hypnotizes her again. They depart for dinner. Justine is waiting outside and hears Marcia give her address. Dave and Phil follow the couple, who've just departed in a cab. First dinner, and a dessert of flaming cherries jubilee. Next on the evening's agenda is a poetry reading at a coffee house where we are treated to the poetic talents of the King of the Beatniks (Lawrence Lipton) accompanied on bongo drums by Eric "Big Daddy" Nord (himself). Afterwards, Marcia and Desmond dance while Dave fumes to Phil. Marcia and Desmond take a cab to Marcia's apartment. Desmond goes in, but he doesnt stay long. Hidden in the bedroom, Justine enters the living room, breaking up the scene of Marcia and Desmond kissing. Justine reveals her part in the game, but not the reason. When Desmond asks, "How many more?" Justine replies, "As long as there are faces like this." Desmond departs and Justine takes over the hypnotic commands. She draws Marcia to the shower and scalding hot water. Dave wants to leave the scene after he notices Desmond leave, but Phil convinces him to stay and talk to Marcia. Before Marcia steps into the shower, Dave interrupts Justine's plan by knocking on the door. Justine lies to Dave and tells him that she and Marcia are old friends from school. Justine awakens Marcia with commands to go along with her story. Dave questions Marcia in the living room. Justine, in the bedroom, senses danger and leaves through the window before Dave can talk to her again. After Justine's departure Marcia returns to herself. They embrace and kiss.
Phil is at home relaxing. He is playing the piano with his dog sitting on top of same. He is wearing a silk, Japanese-style, robe. Dave is outside his door. He picks up the newspaper and rings the bell. Dave confides that he is worried about his girlfriend, "Marcia's changed, she's different. I've never seen her like she was last night." Phil reassures Dave that Marcia's behavior is directly related to her hypnosis. Dave relays the story about the presence of Justine. He describes her as "a real odd-ball." Dave admits that he didn't buy the Justine story. Dave is now convinced that there is a connection with Desmond and the mutilations. He tells Phil he will interview all the women and ask just three questions: 1) Have you ever been hypnotized? 2) Have you ever seen a hypnotist named Desmond? 3) Does the name Justine mean anything?
Dave and Phil pay a call on Mrs. McNear (an uncredited Phyllis Cole), she stuck her face into the blades of an electric fan. The woman refuses to answer the door, but speaks to them through a window. Dave asks his three questions, but all the responses are to the negative. In an agitated state she orders the pair off her property. Dave and Phil walk back to the car. Mrs. McNear opens the curtains to watch them leave. We see her badly scarred face. Their next call is to a woman who drank lye. She responds to the questions in writing, indicating, "I swallowed lye thinking it was coffee. Never been hypnotized." Their next call is to a woman sitting in a darkened room. Her face is scarred. She, like the others, gives the same answers, no, to all the questions. Doris Scott (Carol Thurston) asks for a cigarette. Dave gives her the pack, and retrieves matches from her purse and finds a balloon from the Desmond show. Dave pockets the balloon and lights her cigarette. The glow of the match reveals the woman has no eyes. Once outside, Dave blows up the balloon and confirms it is a part of Desmond's show. He thinks she may be lying, but Phil reminds him that she may not remember as a result of the hypnosis. Phil and Dave decide to ask Dodie the three questions.
Her face now wrapped in gauze bandages, Dodie listens to the doctor explain that multiple plastic surgeries await her but the result will be excellent. While Dave asks Dodie his questions, Phil talks to Dodie's doctor. Dodie, like all the others, replies in the negative to all three questions. When asked about Justine, the doctor volunteers that, "When she was admitted, she repeated that name several times. It seems to terrify her." Phil asks permission to hypnotize Dodie, but the doctor advises against it.
Waiting outside Marcia's apartment, Phil suggests they may learn more when he hypnotizes Marcia to relive her experience with Desmond. Marcia is not in her apartment, so Dave and Phil drive over to the theater. Marcia is back in the audience. Desmond invites the audience to participate in a mass demonstration, "And now I am going to demonstrate to you the power of your own mind." Justine walks on stage with a knife and lemon on a tray. Desmond suggests that their mouth begin to water from the, "sour and bitter lemon." He takes them through a series of physical movements using their arms and hands. After the balloon trick, he pulls the strobe "eye" out of his pocket, "And now, if you dare, look into the hypnotic eye." A woman screams which occurs just as Dave and Phil enter the theater from the back. They spot Marcia near the front of the theater. Justine implores Desmond to stop them. Desmond tries his suggesting voice to stop Dave and Phil, but it does not work. Justine pulls Marcia backstage and up the stairs to the catwalks over the stage. Dave and Desmond struggle briefly over a gun, but Phil stops Desmond. Dave rushes to Marcia, but Justine has taken them both to a swinging section of catwalk. When Phil threatens to shoot, Justine defiantly invites the confrontation promising to take Marcia with her. Phil tries to reason with Justine, explaining that she is young and has a life ahead of her. Justine screams, "What kind of life? What kind of life with my face?" Phil is confused, as Justine is an exceptionally beautiful woman. She reveals her secret, "If you like my face so much, you may have it." At that she pulls off a mask and throws it down to Phil revealing a horribly scarred visage. Phil is distracted, allowing Desmond to get the upper hand. Justine pleads for Desmond to kill Phil, but Dave pulls his gun and kills Desmond. Justine either falls or jumps to her death, landing next to the body of her partner in crime, Desmond. This leaves Marcia dangling high above the stage with Dave trying to pull her back to safety. Marcia wakes and assists with her own rescue. Now safe, Marcia and Dave exit the catwalk. We close with Phil walking out on stage to warn the audience. "Ladies and Gentlemen, a word of warning. Hypnosis, although an important and valuable medical tool, can be extremely dangerous when improperly used by untrained or unscrupulous practitioners. Therefore, never allow yourself to be hypnotized by anyone who is not a medical doctor or has not been recommended to you by your doctor. Not even in a motion picture theater. Thank you."