Dr. Keenan Plain was a surgeon who lost his left arm shortly after finishing medical school. Despite the handicap, he trained himself to become a skilled surgeon. He was bald and had a moustache. Plain claimed that he had studied to be a doctor at the Royal College of Medicine in Chile. While in South America, he befriended the nitrate magnate Mr. Forchune. Forchune was killed by natives, and Plain lost his arm saving Forchune's wife from a similar attack. Dr. Plain's plot was discovered, and while fleeing police he inadvertently set himself on fire and died in the blaze.