The Royal Regiment is a British India story that occurs shortly after the First World War. It revolves around a British Battalion serving in India and chronicles the lives of people who have lived there for most of their lives or are relocating by sea for the first time. The characters include Emily Sheffield, a doctor involved in running a mission hospital on the North-West Frontier, Robin Cuimein, a man born in India returning from war in France to begin an appointment with the Indian Civil Service, and Lily Richmond, a teenage girl who experiences high drama marked with cruelties but also finds genuine love from a young soldier. While exploring these characters' journeys, the story predominantly focuses on the British Battalion's experiences serving "East of Suez".