Haunted by her grandmother's prophecy that she will soon be forced to make a terrible decision, witch Tamsin Greene risks everything to travel back in time to 1887 New York to confront the enemy that wants to destroy her family.

The experiences of high-schooler Savannah, following her decision to take her eight-year-old half brother from his abusive father and their oblivious mother, are interspersed with the earlier story of her mother, Alice, as she meets Savannah's father and unexpectedly becomes pregnant.