Rat Evans, nonbinary heir to one of the oldest magical bloodlines in New York, doesn't cast spells anymore. For as long as Rat can remember, they've been surrounded by doorways no one else sees and corridors that aren't on any map. Then one day, they opened a passage and found a broken tower in a field of weeds--and something followed them back.

When Rat is accepted into Bellamy Arts, all they want is a place to hide and to make sure they never open another passageway again. But when the only other person who knows what really happened last year--Harker Blakely, the dangerously gifted trans boy who used to be Rat's closest friend--turns up on campus, Rat begins to realize that Bellamy Arts might not be as safe as they'd thought. And the tower might not be through with them yet.

Soon, Rat finds themself caught in a web of secrets and long-buried magic, with their friend-turned-enemy at their throat. But the closer they come to uncovering the truth about the tower, the further they're drawn toward the unsettling powers that threaten to swallow them whole.