Haunted by the horrors she witnessed in France during the enemy invasion of 1914, Lady Elspeth Douglas, a titled young Englishwoman, is transformed by her experience and leaves her sheltered life behind to become a nurse and return to the battlefields of France to do her part.

Chaplain Joseph Reavley and his family learn that the identity of the sinister ideologue called the Peacemaker is about to be revealed by a German counterpart, but the family must first solve the mystery of a murdered nurse.