Karou catches us up on the three months since the angels burned Brimstone's doors: Zuzana has a new boyfriend, Karou's kind of pining for the angel who assaulted her, and, oh yeah, Brimstone left her bajillions of dollars in bank accounts, which fund Karou's globetrotting schemes.
Back in Idaho, Karou uses her gavriel to wish for flight.
As she flies away from Bain's cabin, she thinks of a plan.
She's going to talk to Razgut and fly through a portal to another dimension.
It seems that she had talked to Razgut and he told her about the portal he was exiled through. Perhaps the portal works both ways, and she can exile herself on out of this world.