The frightening Boris Karloff 60s thriller with Karloff as a demented doctor using torture for scientific experiments.
Acting
Karloff wheelchair-bound but still commanding, clearly dying.
Production
Mexican sets so garish they become accidental art.

Director
Jack Hill
Trivia, insights & behind the scenes
Karloff filmed this while terminally ill, using a stunt double for standing scenes; he died months after release.
Part of a four-picture Mexican deal Karloff signed for quick cash — the others include Isle of the Snake People and The Incredible Invasion, all released posthumously in 1971.