Fredric March won an Oscar in this version of Robert Louis Stevenson's novel about a scientist who unlocks the evil in his soul.
Dr. Jekyll (Fredric March) lectures that the soul is in two parts struggling with each other; he hopes to separate the two in order to unlock the evil. The saintly doctor inspires a girl to walk without crutches and performs surgery on charity cases. He wants to marry Muriel (Rose Hobart), but her father insists they wait eight more months. Dr. Jekyll rescues a poor woman (Miriam Hopkins) from a ruffian and examines her injury. He recommends rest; she undresses, gets into bed, and then kisses him, asking him to come back. Jekyll's friend Dr. Lanyon (Holmes Herbert) reprimands him. Dr. Jekyll experiments for three days without eating. Then he writes a note to Miriam and drinks the potion. He struggles and changes into a more primitive creature. He declares he is free and laughs. When the butler inquires about the noise, Dr. Jekyll answers the door and says that a Mr. Hyde was there but left by the back door.
Muriel is going away with her father, and Dr. Jekyll must wait. He takes the potion again and finds the poor woman Ivy. He intimidates her and threatens a man with a broken bottle. He gets her an apartment and treats her very badly, saying she belongs to him and threatening her with horror if she disobeys him. Dr. Jekyll throws the backdoor key away and sends Ivy a letter with 50 pounds. He explains to Muriel that he was ill in soul, and she persuades her father to move up the wedding date. Ivy visits Dr. Jekyll, returning the money, showing him her whipped back, complaining of Mr. Hyde, and saying she wants to kill herself. She begs him to save her from Hyde, and he gives her his word that she will not see Hyde again. However, when he sees a cat kill a bird in the park, he spontaneously changes into Hyde. Missing his own engagement party, Hyde tells Ivy about Dr. Jekyll and chokes her to death. He escapes the neighbors but must go to his front door. He is kept out and sends a note to Lanyon to get the vial. Hyde calls on Dr. Lanyon, who insists with a gun that Hyde take him to Dr. Jekyll. So Hyde drinks the potion and changes into Jekyll. After hearing the whole story Lanyon says he is damned; Jekyll promises him he will not mix the drug again.
Dr. Jekyll prays for forgiveness and calls on Muriel to set her free; he dare not touch her, saying he is among the living dead; giving her up is his penance. After changing into Hyde, Muriel screams, and he fights his way out. The police chase him home and find Dr. Jekyll. Lanyon arrives and says Jekyll is their man. Jekyll changes into Hyde, fights the police, and is finally shot, changing back into Jekyll.
Jekyll's frustrated sexual energy that is blocked by
social circumstances is released in a drug experiment that removes
his inhibitions. The result of separating the evil appears to
be far worse than the struggle for the good to control it.