Mary Mack was a beautiful, young, and all-too-soon widow (without the official title) when her Union soldier fiance, Benjamin Watts, disappeared during battle. The tragic event left Mary alone, wearing a black mourning dress for the remainder of her life.

Present day, Mary's spirit has been in mourning for over a century and a half in the town of Cannon Falls, PA. Students sneak into Mack House historic home with lanterns and recite the rhyme anticipating a paranormal encounter with Mary according to town legend. Anna Ipswich, a high school junior, unexpectedly discovers her inner talent to communicate with the Civil War era widow during a visit to Mary's home with Boston Tate, Anna's long-term crush. Anna vows to end Mary's eternal torment and piece together the puzzle of Benjamin's mysterious disappearance.

Can Anna balance high school, the pressure of helping Mary's spirit find peace, and manage a new love story of her own all without losing herself?