
Dr. Jekyll is researching ways to extend human life by creating a potion primarily composed of female hormones. He obtains these hormones from the bodies of young women at one of London’s morgues. Jekyll appears to be onto something when he successfully extends a fly’s lifespan to more than three times its natural length. Encouraged by this success, he takes the next step and tests the potion on himself. The problem? The mixture transforms him into a woman.
Hammer Horror puts its own spin on Robert Louis Stevenson’s famous novel The Strange Case of Dr. Jekyll and Mr. Hyde.

As always with a Hammer production, the film delivers a fantastic visual experience. The atmosphere is spot-on, enhanced by stylish sets, a great musical score, and strong performances. At the helm is seasoned Hammer Horror veteran Roy Ward Baker, a director who knows his craft. The screenplay, adapted by Brian Clemens, is undeniably absurd and might initially sound more comedic than horrific. However, the film holds up well, as long as the viewer can overlook the obvious improbabilities inherent in such a premise.
The best part is the addition of a subplot involving Jack the Ripper, who terrorized Whitechapel in the late 1800s. It provides an entertaining twist on the still-unsolved murders that once spread fear through the streets of London.
Lead actor Ralph Bates delivers a strong performance as the eccentric doctor, while Martine Beswick is equally compelling as his “better half.” Her primary role is to be seductive and alluring—a task she executes effortlessly. Best of all, the two actors share striking similarities, making the transformations between them remarkably effective.