A Map of Days is a sequel to 2015 novel Library of Souls written by Ransom Riggs and fourth book in the series of Miss Peregrine's Home for Peculiar Children.

After receiving a matchbook from Lester Noble Jr., Jacob calls the number and says he wants to continue Abe's work.

Jacob and Emma find a hidden passageway to Abe's cars and, along with Millard, Bronwyn, and Enoch, drive to Mermaid Fantasyland in Florida.

At the Flamingo Manor, they give Billie a package and learn that wights killed most of the ymbrynes in America, leaving mostly demi-ymbrynes.

They fight off the gang "police" from earlier, and Paul agrees to take them to a portal in his hometown, Georgia.

They enter the loop in 1935 and meet Elmer and Joseph, who describe someone named Gandy and show Jacob a photo of a younger H and V, H's travel companion.

She tells them about the Organization, a group of normals who want to eradicate peculiars from the country, and gives him a matchbook bearing a North Carolina address.

At the North Carolina restaurant, they receive instructions to bring a peculiar from a Brooklyn high school to loop 10044.

The group is brought by 1920s gangsters to Leo Burnham, who reprimands the leaders for attending an illegal auction.

Miss Peregrine says the ymbrynes were working on a peace treaty with the Clans, and the group's actions have set them back.

They are exclusively female, often seen as wise and levelheaded figures, and serve as caretakers and teachers of peculiar children usually by creating a timeloop as a sanctuary for them.