A Hungarian gypsy working for a Russian mobster becomes a double agent for the FBI.

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.

A planet is discovered in the same orbit as Earth’s but is located on the exact opposite side of the sun, making it not visible from Earth. The European Space Exploration Council decide to send American astronaut Glenn Ross and British scientist John Kane via spaceship to explore the other planet. After a disastrous crash-landing Ross awakes to learn that Kane lies near death and that they apparently have returned to Earth, as evidenced by the presence of the Council director and his staff. Released to the custody of his wife, he soon learns things are not as they seem.