Mixing the female hormones into a serum and drinking it not only has the effect of changing Jekyll's character (for the worse) but also of changing his sex, transforming him into a beautiful but evil woman.
Susan becomes jealous when she discovers this mysterious woman, but when she confronts Jekyll, to explain the sudden appearance of his female alter ego, he calls her Mrs. Edwina Hyde, saying she is his widowed sister who has come to live with him.
Howard, on the other hand, develops a lust for Mrs. Hyde.
Jekyll soon finds that his serum requires a regular supply of female hormones to maintain its effect, necessitating the killing of young girls.
Burke and Hare supply his needs, but their criminal activities are uncovered.
Burke is lynched by a mob and Hare blinded by lime.
The doctor decides to take matters into his own hands and commits the murders attributed to Jack the Ripper.
Jekyll abhors this, but Mrs. Hyde relishes the killings as she begins to take control, even seducing and then killing Professor Robertson when he attempts to question her about the murders.