 As Widgie and Jen escape into the Post Office Railway, it appears that the entire civilisation is on the verge of disintegration under the assault from the rats.It is worth noting that, seemingly in imitation of "The Lord of the Rings" (1937 and 1949), Leonard includes appendices relating the aftermath of the story underground, in which the Railwaymen and Canal Folk discuss the joint threats of the children and the rats, and giving a short history of the North London System (and suggesting that similar societies exist beneath many major cities, at least in England).It also includes two short "Interludes", set aboveground, concerning the search for the missing children.