Armed with secret knowledge, Juliette, now mayor of Silo 18 and her crew set out to rescue a world she hates but now understands better -- the world of the Silos with its rigid rules and terrible consequences for disobedience.

In a ruined and toxic landscape, a community exists in a giant silo underground, hundreds of stories deep. In a society full of regulations meant to protect the community, Sheriff Holston, unexpectedly breaks the greatest taboo of all: he asks to go outside. An unlikely candidate is appointed to replace him: Juliette, a mechanic with no training in law, whose special knack is fixing machines. Now Juliette is about to be entrusted with fixing her silo,...