Dr. Jekyll and Sister Hyde (1972)

In foggy London Dr Jekyll experiments on newly deceased women determined to discover an elixir for immortal life. Success enables his spectacular transformation into the beautiful but psychotic Sister Hyde who stalks the dark alleys of Whitechapel for young, innocent, female victims, ensuring continuation of the bloodstained research. With each transformation Sister Hyde becomes the more dominant personality, determined to eventually suppress the frail, ineffectual Dr Jekyll forever.