Boris Karloff, as usual, is a joy to watch, as is Christopher Lee, who was right on the verge of becoming a big star in the Hammer films. This film is also notable for strongly evoking the grimy atmosphere of those out-of-the-way areas in 1800's England, worthy of comparison to David Lean's "Oliver Twist" (1948). Coincidentally, not long after seeing this film I happened to read the true life story of Horace Wells (1815-1848), a Connecticut dentist who experimented on himself with ether, chloroform, and laughing gas in an effort to discover a painless method of oral surgery. He succeeded, but became an addict in the process; his behavior subsequently became so violent that he was placed in prison, where he committed suicide. I wonder if Karloff's character in this film is at least partially based on Horace Wells.