"By April 1916, the fervor that accompanied war's outbreak has faded. In its place is a grim reality. Throughout Germany, essentials are rationed. Hope, too, is in short supply. Anna Zeller, whose fiancé, Bruno, is fighting on the western front, works as a nurse at an overcrowded hospital in Oldenburg, trying to comfort men broken in body and spirit. But during a visit from Dr. Stalling, the director of the Red Cross Ambulance Dogs Association,...