Indecent Obsession by Colleen McCullough
The dutiful and disciplined Sister Honour Langtry has sole charge of Ward X of a military hospital in the Pacific, where she cares for soldiers who have gone 'troppo' or are battle fatigued. War with Japan has only been over a few days when into this intense, confined world comes a new patient, Sergeant Michael Wilson. Immediately, his arrival transforms Ward X into a pressure cooker of emotion leading inexorably to tragedy for Sister Honour Langtry, as she is torn between her duty to all her patients - and her love for one of them...