Former Scotland Yard detective Captain Sam Wyndham starts a new life in Calcutta in 1919 desperately seeking to escape the horrors of the Great War. Yet before he can even acclimatise, he is appointed the head of a new CID and tasked with investigating the murder of a senior British official. With the aid of Indian-born Sergeant “Surrender-Not” Banerjee, Wyndham embarks on a journey into the dark underbelly of the British Raj to find the killer.