The original took serious liberties with the source material, and Hammer films were threatened with a lawsuit if any of it's story or images were copied. So, we are left with the elements brilliant and privileged scientist, taking science too far, creation of a monster, and bad consequences. Mix elements thoroughly and bake for 45 minutes and you get a new version of Frankenstein. Or Jekyll and Hyde. Same deal.
TCM played a pile of Christopher Lee films a couple weeks after his passing. Because interesting films on TCM come in waves, I had filled my DVR with good stuff and had to be very selective what I saved. This was the lone Lee film that made the cut.
Formal, stilted acting, mostly unoriginal story, and a complete lack of actual scares or surprises is mostly saved by decent set design and photography, and Lee's performance. Very much a Hammer production. AMRU 3.5.
Christopher Lee: "I've got no lines!"
Peter Cushing: "You're lucky. I've read the script."