Two weeks after an unexplained illness begins spreading through the Muggle world, Hogwarts is forced into an unimaginable fight for survival. As the infection breaches the wizarding world, ancient magic, lifelong rivalries, and fragile alliances are put to the test. Trapped within the castle walls, eight Slytherins must decide how far they’re willing to go to survive—before the people they love become the very monsters hunting them.