Alice was pulled into hiding at The Library by Christopher Plover. That Christopher Plover. The one who wrote Fillory and Further, and also molested the future "Beast." He wants her to help him do a spell in exchange for his helping her to find her book and escape from the Library. Ewwwww.
Margo tells Josh to buck up and find a solution to his problem. Basically, he needs to pass along his STD from hell or die trying. They consult some books, and he talks to a former one-night-stand named "Isaac" who, yes, also now was the murder-STD.
In Fillory, Julia and Penny find one of Bacchus' former maenads in despair. They ask if she can help them determine what is happening with Julia and her goddess-ness. She runs some tests, and then says she needs a devoted follower to perform an intimate ritual in order to learn more. Penny is that devoted follower.
The ritual proves that Julia is still a goddess. And yes, it looks like Penny has a mega-thing for her since this is alternate timeline Penny who was in love with alternate timeline Julia. And yes, now she has a maenad follower.
After his many efforts with Margo fail, Josh locks himself behind bars in a cage. He has to have sex to pass along the werewolf sickness, and he doesn't want his urges to make him attack or kill anyone. Though they will make him destroy himself if he stays behind bars.