Seventeen-year-old Rosefinch has been traveling along the weather-beaten coast for two years on a quest to find a witch strong enough to help her control her magic. Her magic is volatile, hard to wield, and Rosefinch is tired of the pain of magical backlash. When she's directed to the sea-side village of Harp, she discovers the ancient castle of a long-lost Witch Queen with the inhabitants long gone; the only remaining soul is a knight encased in solid ice guarding the door.

When she attempts to lift the curse, she frees Thierry, a human with no memory of who they are, wrapped in cursed magic so strong that they cannot leave the castle. Thierry is soft spoken, strong, and in possession of a fey sword that should be impossible for them to have. But they have secrets of their own, as do other members of the Harp family still hidden within the walls.

Harp castle was left in ruins for a reason, and Rosefinch must find a way to cure the curse or lose Thierry—and the chance to learn the truth about the Witch Queen—forever.