India, 1919. Desperate for a fresh start, Captain Sam Wyndham arrives to take up an important post in Calcutta's police force. He is soon called to the scene of a horrifying murder. The victim was a senior official, and a note in his mouth warns the British to leave India - or else. With the stability of the Empire under threat, Wyndham and Sergeant 'Surrender-not' Banerjee must solve the case quickly. But there are some who will do anything to stop them.