A group of medical students observe Dr. Daniel Jekyll perform brain surgery at Our Lady of Pain and Suffering Hospital in Los Angeles, California. Meanwhile, Hubert Howes, the world’s richest man, watches a recording of the procedure from his hospital bed, hoping to recruit Jekyll to perform the world’s first “total transplant,” replacing every organ at once. However, Dr. Jekyll announces his retirement from surgery, intending to research medication that will eliminate mankind’s need for operations. Howes threatens to blow up the hospital if his procedure does not occur as planned. As a result, Dr. Carew, hospital overseer and Jekyll’s future father-in-law, forbids Jekyll from marrying his daughter, Mary, if he does not comply with Howes’s wishes. Jekyll attends to patients in the charity ward when Mary visits, complaining that he missed their lunch date because he was working. She reveals that she submitted Jekyll’s experiments for a $50,000 research grant, but Jekyll is upset that she shared his private work without his permission. Outside, they see plastic surgeon Dr. Knute Lanyon, who flirts with Mary and notices that Jekyll looks tired. After Mary leaves, Jekyll observes the dead mice test subjects of his failed drug experiments; just as he is about to start over, a nurse calls Jekyll away to perform an emergency procedure on a patient named Ivy Venus. Ivy flirts with the doctor and invites him to visit her at the nightclub where she works. Later, Jekyll returns to his work, measuring two white powders on a square mirror. Exhausted and unable to focus, he drops the powders on the table, ruining his experiment, but creating a sparkly mixture. He falls asleep and accidentally inhales the powder, causing him to thrash and spasm wildly. Jekyll’s body transforms, growing chest and facial hair, elongating his genitals, and producing gold jewelry on his ears, fingers, neck, and teeth. With an air of wild confidence, he bags more of the powdered drug, steals a car, and drives erratically to Ivy’s club. After Ivy performs onstage, she takes him to her room backstage and undresses. He introduces himself as “Hyde,” and they have sex. The next morning, the man wakes up, returned to his original state as Jekyll, and regrets his actions. He drives to Mary’s equestrian academy just as she is about to compete in a horse-jumping competition; Jekyll runs alongside Mary’s horse and declares his unwavering love. Back at the hospital, Hubert Howes meets a prospective testicle donor, offering $1 million for both of the man’s organs. Jekyll attempts to flush his drugs down the toilet, but decides to save the substance and inhales more. Transformed into Hyde once again, he hijacks a van and finds Ivy at the grocery store. Jekyll wakes up in the van hours later, lying naked between Ivy and another man. Horrified, he sneaks into Mary’s bedroom at her parents’ estate, surprising Mary with his sexual advances. Before he and Mary make love, her father barges in and holds Jekyll at gunpoint. Jekyll concedes to perform the surgery for Howes, and Dr. Carew grants Jekyll and Mary permission to have sex. At the hospital the next day, Jekyll declares “a new beginning,” but again hesitates to dispose of the drugs. Although Dr. Carew flushes the packet down the toilet, Jekyll becomes erratic during surgery, looking at the nurse’s breasts in her low-cut uniform. As Jekyll slowly transforms into Hyde, he throws Howes’s donated organs into the air and leaves the operating room, forcing Dr. Carew to continue the procedure by offering the use of his own body parts. Interrupting Lanyon during a breast augmentation, Jekyll exposes his changed appearance. When Lanyon reveals that he wears women’s underwear, Hyde throws himself out the window and returns to his laboratory. He receives a telegram informing him that he won the research grant, and has been invited to a ceremony in London, England. Hoping to use the money to buy Ivy’s affection, Hyde finds her at an arcade and invites her to accompany him on his trip. However, she admits she is not interested in Hyde because she likes Jekyll. When he reveals that they are both the same man, she does not believe him; in his frustration, he destroys an arcade game, and Ivy is electrocuted. Hyde travels to Los Angeles International Airport and climbs onto the back of an airplane headed for London. Meanwhile, Ivy revives, and travels to London via train and boat, vowing her revenge. At the ceremony, Mary and Lanyon sit in the audience, expecting Jekyll to arrive before the presentation begins. Lanyon comments on Jekyll’s “sexier” appearance the last time he saw him, and reveals that he hates women. After the presenter announces Jekyll’s achievements “harnessing the power of animal instinct within man,” actor George Chakiris accepts the award on the doctor’s behalf, declaring that the remaining vial of Jekyll’s substance will be donated. Hyde swings down from the balcony with spiky hair and a frizzy mustache, grabbing the microphone and singing. Realizing that Hyde is the same man as her fiancé, Mary becomes aroused by his new personality. Hyde removes his pants, runs out of the hall and is chased through the foggy streets through by the audience members. Ivy joins the crowd, and they follow him until he falls off the side of a building. As Ivy and Mary kneel next to Hyde’s body, he transforms back into Jekyll. Upon waking, he claims that the drugs have exposed the two sides of his split personality. Mary desires Hyde, while Ivy wants Jekyll, and the two women drag him through a cemetery, agreeing to work out an arrangement. Nearby, the skeletal corpse of Robert Louis Stevenson rolls over in its grave.