Last Order begins when Alita is resurrected by Desty Nova's nanotechnology in the floating city of Tiphares. The city's dark secrets are brutally exposed, but it turns out to be a small part of a complex world. Going into space with new and old companions alike, to look for her lost friend Lou Collins and to find out more about her forgotten past, Alita is caught up in an interplanetary struggle between the major powers of the colonized solar system. Along the way, she forms an alliance with three of the Alita Replicas who have now begun to think for themselves, an unsavory superhacker, and Nova himself when she enters the Zenith of Things Tournament (Z.O.T.T.), a fighting competition held every ten years. During the course of the story, more background about the setting of Battle Angel Alita that was not disclosed in the prior series is revealed, such as how the Earth emerged from a cataclysmic impact winter that wiped out most of the population.

-- Wikipedia