From Amicus Productions, and based upon Robert Louis Stevenson's Dr. Jekyll and Mr. Hyde, albiet very loosely based. This is a good horror film with a good lead performance, and at a mere 77 minutes long. It doesn't outstay it's welcome either, but it has some genuine scares for it's day. It has wealthy psychologist Dr. Charles Marlowe (Christopher Lee) inventing and experimenting with a new drug that will reveal the inner inhibitions of his patients. The effects are varying, from bringing out their opposite personalities and revealing childhood traumas. However, Marlowe sets about in testing the drug upon himself, and it brings out a mischievious side, as well as an alter ego, Edward Blake. However, his colleagues, Frederick Utterson (Peter Cushing) and Enfield (Mike Raven), begin to worry for the wellbeing of Dr. Marlowe, especially as his will has been rewritten to include Edward Blake. Meanwhile, things have gone from bad to worse for Dr. Marlowe, he's addicted to the drug, and he's become a murderer under the guise of Blake, and the antidote isn't working either. It's quite dark, but it's a good film, maybe one of Amicus' best, and some of it is a bit silly, almost marred by a cat being murdered after being given some of the drug, but Lee relishes the dual role really well. But, it did chicken out of being more faithful to Dr. Jekyll and Mr. Hyde, which is a shame.