Battlefield nurse Bess Crawford returns from France for a well-earned Christmas leave and finds a bruised and shivering woman huddled in the doorway of her London flat. Concern and a firm sense of duty compel the independent and compassionate nurse to be see that the woman is safe. But when she arrives at the woman's house, Bess is unsettled by the tense atmosphere. Before she can understand what is going on, matters take a deadly turn.