India, 1921. Captain Sam Wyndham is battling a serious addiction to opium that he must keep secret from his superiors in the Calcutta police force. But Wyndham finds himself in a tight spot when he stumbles across a corpse in an opium den. When he then comes across a second body bearing the same injuries, Wyndham is convinced that there's a deranged killer on the loose. However, revealing his presence in the opium den could cost him his career.