Jem is an orphan living in the floating city of Cirrus. As the dreaded Horn attack, Jem and his friends are scooped up in the adventure of a lifetime when the floating orphanage, Janus, is destroyed. Not only must Jem, Crowen, Kaetu, and a mec named Goat survive aboard a Horn capital ship, but they must find a way to save each other and all of Skye. In order to do so, Jem and his friends soon find themselves in the crosshairs of the two greatest fleets ever assembled, with a battle coming that may bring nightfall upon Earth forever. But there is hope in a well-kept secret buried beneath a mountain far below in the Land left devastated by the two-hundred year-old holocaust.