45 Bagian Sedang dalam proses Cassia Brightberry's Ancient Magic is growing stronger, yet she can't control it. Each manifestation is more destructive than the last, and she worries something catastrophic will soon happen. She returns to Hogwarts for her sixth year, hoping the Keepers will finally provide the training she needs. However, they seem just as reluctant as before, and Cassia is left to figure it out herself until mysterious letters appear, giving instructions on how to harness her incredible power.
Meanwhile, reports of vicious beasts are becoming increasingly common, and Hogwarts tightens its security as the attacks draw ever closer to the school. Cassia and her friends have a terrible feeling it's connected to her in some way, urging her to develop her magical prowess ever more quickly. She finds mentorship in Hypatia Herbert, the enigmatic Alchemy professor with a quest of her own, and whom Cassia isn't sure she trusts entirely. But she can't deny Professor Herbert possesses valuable knowledge that will guide her through her challenges.
Cassia swiftly realizes this won't be the "less-exciting" year she'd wished for. But perhaps-despite the danger of it all-she and her friends can remedy their previous wrongs and heal from the devastating consequences weighing over them, turning from darkness into something brighter.