Some of these pictures and descriptions may give away plot details that you might not want to know before watching the film.
This is a very imaginative Hammer Studios version of the Jekyll and Hyde story originally written by Robert Louis Stevenson. It adds Jekyll's cheating wife who Hyde tries to win over because he is attracted to the bad part of her personality that cheats on Jekyll and hides it from him. It also adds a sexy snake dance and other Technicolor nightlife.
In London 1874, Dr. Henry Jekyll is a reclusive scientist, an outcast to his colleagues, who writes that he lives a life of frustrated isolation and loveless misery. He believes that two forces struggle for supremacy in every human personality; man as he could be - beyond good and evil, and man as he would be - free of all the restrictions society imposes on us. He develops a drug and injects himself with it to bring out the unrestricted man in his own personality. He loses his bushy eyebrows, beard, and low voice and turns into Edward Hyde, a well-dressed handsome and confident ladies man. (Where can I get me some of this drug?) Hyde goes out on the town and meets Jekyll's good friend Paul Allen (Christopher Lee) who is having an affair with Jekyll's wife Kitty (Dawn Addams.) The two men explore the dark side of London's entertainment, including an opium den and a nightclub where they watch an exotic dancer named Maria take a Boa Constrictor out of a basket then dance with it draped around her shoulders. She puts it down on the floor and dances around it then finally ends her performance by her putting the snake's head into her mouth. Hyde gets turned on by the dance and immediately goes to meet Maria in her apartment backstage where he sees the snake in a cage and comments that it guards her constantly. She tells him to leave it alone because it's dangerous, then takes Hyde to bed.
Bitter with jealousy of Paul and angry because he could not seduce Kitty, Hyde is determined to get revenge on them. He invites them to Maria's apartment where he locks Paul into the snake's room where the snake is out of its cage and Paul is killed by the snake. (In movies, all snakes are deadly, even a harmless little boa.) Kitty is so shocked when she finds his body that she falls over a railing to her death.