Scientist Dr. Henry Jekyll (Bates) is working on a serum to prolong life, a concoction based on female hormones.

But when he tests it on himself, he turns into...lovely Martine Beswick!

Dubbing his female side "Sister Hyde," Jekyll finds he needs more estrogen in order to keep his "sister" alive, so he then goes on a murderous spree, slashing poor hookers and draining them of their precious feminine juices.

Set in foggy Victorian London, this one features great costume and period design. But it's real strength is in its lead performances; Beswick and Bates give inspired turns, clearly revelling in the wholesale enjoyment of the solid, gender-bending screenplay (written by Thriller scribe Brian Clemens, incidentally).

The supporting cast is nothing to sneeze at either, especially Brodrick and Fiander as Jekyll's hopelessly manipulated, bewildered upstairs neighbors.

Excellent all around, with a wonderful score by David Whitaker.