Marietta Hughes is a spy for the Union, a family tradition that she embraced with some reluctance. Shade Osborne is a Pinkerton agent who has infiltrated the Knights of the Golden Circle, a Confederate spy ring that is meeting in a secret hideaway located under Marietta's home. The discovery of the Golden Circle's meeting place and their plans to destroy the Union tilts Marietta's world on its axis. Having lost her husband and brother during the war, she no longer knows whom she can trust. Her blossoming romance with the dashing Shade is overshadowed by worry about his trustworthiness.