Determined to develop a gaseous drug that allows patients to tolerate the difficulties of surgery, Dr. Bolton (Boris Karloff) devises numerous opium-based remedies, which he tests on himself. His experiments fail miserably in trials performed for his colleagues -- who include his own son, Jonathan (Francis Matthews) -- and Bolton is dismissed from his position. Having developed an addiction to opium, Bolton finds work treating the poor but falls in with grave robbers in order to get drugs.