April 1916, Germany: 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, she witnesses a rare spark of optimism: as a German shepherd guides a battle-blinded soldier over a garden path, Dr. Stalling is inspired with an idea—to train dogs as companions for sightless veterans.

Anna convinces Dr. Stalling to let her work at his new guide dog training school. Some of the dogs that arrive are themselves veterans of war, including Nia, a German shepherd with trench-damaged paws. Anna brings the ailing Nia home and secretly tends and trains her. In Max Benesch, a Jewish soldier blinded by chlorine gas at the front, Nia finds her person.

War has taken Max's sight, his fiancée, and his hopes of being a composer. Yet despite all he's given for his country, the tide of anti-Semitism at home is rising, and Max encounters it firsthand in one of the school's trainers. Still, through Anna's prompting, he rediscovers his passion for music. But as Anna discovers more about the conflict's escalating brutality—and Bruno's role in it—she realizes how impossible it will be for any of them to escape the war unscathed . . .