War is devastating, especially when family members fight on opposite sides. That is the scenario of The Marriage Tree. It is the story of two families, the Conroys and the Ulsters, during the Civil War. Liam Conroy and Evangeline Ulster secretly marry as the war commences. Liam, fighting for the North, is killed early in the conflict by Evangeline's brother Ewell. Evangeline then becomes a spy for the North. She spends the next several years, against the backdrop of battles and important personalities, with a dual purpose: to honor her husband by helping the Union to win the war and to bring the Conroy and Ulster families to reconciliation.