The Hammer movies has never been considered high art by any means, but the effective use of clichés (amazing Victorian characters and sets, to name one) and clever filming and editing continue to be fun to watch. The company is still around.
Dr. Jekyll is looking for an elixir of life and realizes that giving flies female hormones make them live longer. They also turn males into females.
Planning to use himself as a human test subject Dr. Jekyll has to get hold of bodies of women to get access to said hormones, and while he starts out buying corpses provided by grave robbers it all soon escalates into murders of the Jack the Ripper kind.
Dr. Jekyll and Sister Hyde does have some crossdreamer qualities. The first transformation scene is clearly an erotic one, and much more explicit than the clip below may indicate. The movie also makes use of a trope from TG fiction, where the female personality - sexy, alluring and obsessive - threatens to take over completely.
All in all it is not a bad movie, as far as B movies go. Do not expect realism, though. It takes only 30 seconds from the doctor drinks a glass of female hormones until "Sister Hyde" takes over. We wish!
