Baker, whose other directing credits include the wonderful "Asylum," made this inevitable gender-bending take on the Jekyll-and-Hyde story, with Bates as a good doctor whose new female hormone serum turns him into the sinister woman who calls herself Hyde, played by Bond girl Martine Beswick (from "Thunderball") who does look a lot like Bates.
Despite its Ed Wood-esque concept, the film does deliver some outstanding Hammer thrills and is way better than the average Jeckyll-Hyde film. Beswick gets off on seducing men and she does look sexy draped on those old English chairs. It's an extension of the concept Hammer explored with "The Two Faces of Doctor Jeckyll," when Jeckyll became a suave, good-looking Mr. Hyde. Now Mrs. Hyde is a gorgeous, voluptuous, seductive, intoxicating and deadly female.
In addition to the gender-bending twist, it also adds a Jack the Ripper-style storyline later in the film -- and is actually one of the best films of that subgenre to have shown up in the '70s. The movie was actually PG when it came out in the U.S., but the European cut boasts more breasts and blood. Despite its fun exploitative concept, great costumes and the historic English setting, many Hammer fans also view it as a film that came out of a lesser era of the film company. But it is a solid offering from the film company, and like many a decent horror film can really be viewed as a story about insanity and addiction.