There are exactly one hundred halls of magic to choose from. Ever since our parents were killed I knew exactly which hall was for me. Aurelia "Aurie" Silverthorne is one of the best and brightest to ever apply to the Hundred Halls, the only magical university in the world. To be accepted, she must pass grueling trials that claim the lives of aspirants every year. But more than her desire to practice magic is at stake. Aurie's little sister has been courting powerful forces in hopes of protecting herself from the beings that killed their parents, but alliances come with complications. As things spiral out of control, and dangerous foes arise at every turn, Aurie knows the only way to protect her sister is to pass the trials—even if it means making a terrible sacrifice.

Whoever controls the Hundred Halls, controls the world. Aurelia "Aurie" Silverthorne has high hopes for her second year in the Hundred Halls, the world's only magical university, but her expectations are destroyed when she accidentally unleashes a plague of faez-eating thralls and spends week after week getting killed in the Grand Contest. But none of this matters when Aurie learns that the Cabal searches for a powerful magic that will help them get control of the Hundred Halls. If Aurie can't stop them, then passing her classes will be the least of her worries.

In the Hundred Halls, students experiment with all manners of catoptromancy, lexology, verumancy, rune spells, demonology, shape changing, and a thousand other arcane techniques. Every magic is encouraged. Every magic, except one—soul magic. As Aurie's third year begins, students are found without their souls, ripped from their bodies, leaving them empty husks. Someone, or something, is stealing them for a nefarious purpose. With that kind of power being collected, not even the professors are safe. If Aurie and her sister cannot stop the soul thief before the end of the year, the Hundred Halls will never be the same.

Every fall the city of Invictus bustles with new students, and the classrooms reek of spent faez. This year it's true of every hall except one—Arcanium. While Semyon Grey, the Patron of Arcanium, slowly heals from his soul being torn, no one in the Hall can practice their craft, leaving them defenseless against the Cabal and faez madness. The Silverthorne sisters must find a way to speed up the healing, or the Hundred Halls won't survive the year. But everything they try only makes things worse, until they're left with an impossible decision that may cost the sisters their lives.

As the Hundred Halls heads towards civil war, the fate of the city—and possibly the world—depends on Aurie and Pi finding the truth about Invictus' disappearance. Following a trail of dangerous clues, the sisters delve deeper into the head patron's past, finding their family's history entwined with the university. As they get closer to the final answer, they must decide if saving the world is worth shattering the ideas of who they think they really are.