London in the 1840s is the setting for this British horror film starring Boris Karloff as Dr.Thomas Bolton, an eminent surgeon determined to discover an effective anaesthetic to relieve his patients suffering. Unusual for its time, the film deals with the consequences of drug addiction, Boris Karloff gives one of his finest performances as the Doctor experimenting on himself who becomes addicted and finally destroys his own career in his relentless pursuit of the elusive anaesthetic gas. Much of the story takes place in the slum area of old London known as the Seven Dials, hence the film's original title The Doctor of Seven Dials, a curious mix of horror and historical drama.