As Ulysses S. Grant and Robert E. Lee lock horns across the Virginia countryside in the spring of 1864, Lyons and Cormac O'Connor enlist in the Union Army, concealing a dangerous secret. When a battle wound lands Lyons in a field hospital, Major Jonathan Hart, a weary regimental surgeon, and his nurse, Sarah, discover the truth: Lyons is a woman. Affection grows between the surgeon and the nurse as they struggle to keep Lyons out of the clutches of Grant's rapacious war machine. Their story comes to a devastating climax amid the carnage of Cold Harbor. Drawing on hidden history and the overlooked role of women who fought, Soldier for the Union weaves together themes of trauma, healing, and the fragile bonds that sustain us in our darkest hours. Rich in historical detail while vividly rendering the realities of Civil War medicine, Soldier for the Union honors the courage of those who chose to heal rather than destroy and offers an unconventional perspective on the conflict.