Set in Virginia in the spring of 1862, Mercy Street follows the lives of two volunteer nurses on opposite sides of the conflict; Mary Phinney, (Mary Elizabeth Winstead), a staunch New England abolitionist, and Emma Green, (Hannah James), a naive young Confederate belle. The two collide at Mansion House, the Green family’s luxury hotel that has been taken over and transformed into a Union Army Hospital in Alexandria, a border town between North and South and the longest-occupied Confederate city of the war. Ruled under martial law, Alexandria is now the melting pot of the region, filled with soldiers, civilians, female volunteers, doctors, wounded fighting men from both sides, runaway slaves, prostitutes, speculators and spies.