It is February 1947, and England, having survived six years of war, is in the grip of the most severe winter in living memory. At 'the Hut', the ex-Army encampment that serves as the main country base for the still war-damaged St Martha's Hospital, London, spirits remain high despite snow-blocked roads, power cuts and shortages of everything, including staff. Back from the war are Sam Lincoln Browne, medical registrar, an ex-POW of the Japanese; Hoadley East, Senior Surgical Officer, ex-6 years in RAMC; Caroline Carr, theatre staff nurse, ex-2 years in QAIMNSR. The defensive layers the war had taught these young people to form are stripped bare when a diphtheria epidemic threatens.