Charles Marlowe becomes I, Monster. I, Monster comes from director Stephen Weeks and writer Milton Subotsky. It's a version of Robert Louis Stevenson’s The Strange Case of Dr. Jekyll and Mr. Hyde, featuring Christopher Lee, Peter Cushing, Mike Raven, Richard Hurndall, George Merritt, Kenneth J. Warren, Susan Jameson, and Marjie Lawrence. Carl Davis composed the music, and Moray Grant handled the cinematography. Kept By The Power Of God! Stevenson’s familiar story receives another adaptation as Dr. Charles Marlowe (Lee) develops a drug meant to release his patients' restraints. However, when he tests it himself, Marlowe transforms into the monstrous Mr. Blake, who grows increasingly cruel and unrestrained with each change. Dull and Hyde! Amicus never really achieved the level of success in British horror they hoped for; some films are enjoyable, and there’s decent value to be found in segments from their collections of stories, but many just feel like feeble attempts to find a place in the market. There were often good ideas behind the writing, as with I, Monster, which has respectable literary goals. The Eastman Color photography is pleasing, the period details are well done, and using tilted camera angles was a smart choice, but unfortunately, the film suffers from being too dull and having other issues. The first thing that strikes you is Cushing and Lee, two major figures in British cinema and cornerstones of horror. Lee doesn’t seem right for Mr. Blake; it's not helped by the makeup, which would be more appropriate for a Carry On Screaming film. With Cushing, the problem is simply that he isn’t used enough, something unforgivable for a horror movie trying to have intellectual depth. Carl Davis’ musical score is terrible; at times it sounds like it belongs in a silent comedy. Originally planned as a 3-D project, that idea was dropped early on, and it's difficult to imagine that the gimmick would have prevented it from being the depressing film that it turned out to be. 4/10

Source on TMDB