Karloff stars as Dr. Thomas Bolton, a humanitarian London doctor who is attempting to develop a feasible anesthetic for the pain and suffering of surgery in the days when hospitals were like torture chambers. Unfortunately, he experiments on himself and slowly becomes addicted to drugs.
Thinking he has found a proper anesthetic, he performs a demonstration of his pain-killing gas in an operating theater full of physicians and students. Unexpectedly, the gas wears off too soon; the patient awakens during the operation and bolts from the table, attempting to attack the audience.
Karloff is fired from his position and begins to become desperate for drugs, now that his...