When battlefield nurse Bess Crawford returns from France for a well-earned Christmas leave, she 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 certain the woman is safe. But once 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 when another of the houseguests is murdered.