Penny makes it to the Underworld where he is led to Benedict. The mapmaker says he no longer has the key, but he knows who does: The Librarians. Making his way back towards The Library, Penny runs into his old boss Victoria, who reveals she knows Penny’s plans--through “his book.” He is then led to meet the writer of everyone’s futures and comes to find they mysteriously look like Alice. Desperate for a clue to key, Penny reads his friend’s sagas as they are written, eventually identifying where the key. While he does manage to find it (back with Benedict), he is crossed by Victoria on behalf of The Library in the process.

Back at Brakebills, Irene stops by to get that favor from Julia, and a recently appeared Fen sees Irene’s companion: a slave fairy. Fen and Julia press the fairy, named Sky, about what she knows and they ultimately unearth Irene’s horrible and bloody secret. The also learn the truth behind the white magical powder. Meanwhile, Kady, Harriet, Poppy, Quentin, and Olivia make a mirror bridge to The Library, despite Alice’s reluctance to help. But once there, things go south almost immediately. Penny hasn’t dropped the key yet, Alice appears and seems to be working with The Library, and Harriet reveals her familial relationship to the head librarian, Zelda. In the end, Alice comes up short, Quentin no longer trusts Alice, Poppy bales on everyone, Kady loses Penny (again), and Harriet’s time on the show comes to an end.