"Dr. Bolton continues his search for the exact formula to produce an effective anesthetic, experimenting on himself. Eventually, the doctor becomes addicted to his own inhalation of chemicals used to produce the anesthesia. He finds himself in a crime-ridden and disreputable area of London known as 'Seven Dials', where people are purposely being murdered so that their bodies can be sold to the hospital for money. Dr. Bolton uses these thieves and cut-throats to provide him with the chemicals he needs to continue his anesthesia experiments while writing fraudulent death certificates for those who are being murdered in 'Seven Dials'. Doctor Bolton is in a downward spiral of addiction, and the necessity to procure the drugs he needs to continue his experimentation. It is clear that the doctor is on the path to destruction, but watch the ending to see how things may or may not come right in the end. Boris Karloff is at his best in this role, and exhibits a wonderful and convincing performance throughout. A timeless Karloff classic for sure!