Resigned to living out the Second World War in a German POW camp, James Hunter, an English officer, begins studying a pair of redstarts near the camp. His interest in the birds captures the attention of the Kommandant and gives James cause to fear for his life. Meanwhile, back in England, James's young wife, Rose, falls headlong into a passionate affair with another man. When James's sister, Enid, is bombed out of her London flat, she comes to stay with Rose, and the two women form a surprising friendship that alters the course of both of their lives.