Smoke and Ashes by Abir Mukherjee

India, 1921. Haunted by his memories of the Great War, Captain Sam Wyndham is battling a serious addiction to opium that he must keep secret from his superiors in the Calcutta police force. When Sam is summoned to investigate a grisly murder, he is stunned at the sight of the body: he’s seen this before. Last night, in a drug-addled haze, he stumbled across a corpse with the same ritualistic injuries. It seems like there’s a deranged killer on the loose. Unfortunately for Sam, the corpse was in an opium den, and revealing his presence there could cost him his career… Read more.