The Magicians (The Magicians #4)

After discovering carnage in the midst of the Brakebills library, it's clear that there is something much bigger at hand than the rivalry between the hedge witches and the traditional magicians. Someone, or ?something sinister is at work, and Dean Fogg will finally have to reveal the truth behind opening the doors of Brakebills to the hedges... and what it means for their future.