Bob is initially reluctant to give out such dangerous information, but eventually tells Harry that immortals can be killed during certain conjunctions, such as on Earth on Halloween night, the day after tomorrow.
In trying to figure out how to proceed, Harry consults with many magical powers, including Donar Vadderung, Lily, Titania, the Faerie Mothers, and Rashid.
Harry learns that Outsiders are constantly attempting to get past the Outer Gates, which are defended by the Winter Fae.
Harry and his friends head for the top of the island, where they find Lily and Maeve magically assaulting Demonreach.
The mantles of the Summer and Winter Ladies pass respectively to Sarissa and Molly, and Mab departs with both of them to begin training them in their new duties.
Harry decides to remain on the island for the time being so that he can learn more about it and establish a new base of operations, and takes a branch from its oldest oak tree to use in making a new staff.