Sunreach Skyward Flight recap

With Spensa away and Detritus newly shielded, the Defiant Defense Force has hyperdrives for the first time, in the form of taynix, the teleporting slugs Spensa brought back from Starsight. There are nowhere near enough of them. FM and the engineer Rodge take on the work of finding more in the caverns of Detritus, learning to coax and care for them, and discovering that different varieties do quite different things. The program pulls FM into a fight she did not expect, over how much the National Assembly is entitled to keep from the people it governs and who really commands the DDF. When a Superiority force moves against Detritus, the new ability to jump ships in and out of a battle proves decisive, and humanity ends the book mobile rather than besieged. FM and Rodge come together, and Alanik, able to travel again, departs for her own world to try to keep it out of the Superiority's hands.

Previously: humanity survived on the caverned planet Detritus, penned there by an alien government called the Superiority and raided by its unmanned drones. Spensa Nightshade fought her way into the Defiant Defense Force, recovered an advanced starfighter with an artificial intelligence called M-Bot, and turned out to be cytonic, able to hear across space and teleport a ship. She infiltrated a Superiority fighter program on the space platform of Starsight, where she learned that faster-than-light drives are living creatures, taynix slugs, and that the program's director Winzik intended to control the world-killing entities called delvers rather than defend anyone from them. Winzik drew a delver to Starsight; Spensa met it mind to mind, persuaded it to leave, and escaped with a hoard of taynix. Detritus gained hyperdrives and a shield of reactivated orbital platforms, Winzik gained a fleet and emergency powers, and the cytonic alien Alanik, shot down over Detritus earlier, has woken up on a planet not her own. Jorgen has proved to be cytonic himself, and Spensa has since left to chase the delvers' origin, out of contact and not expected back soon.

Detritus is shielded and can, in principle, jump ships between stars, but only a handful of taynix have been found and nobody understands them. FM flies with Skyward Flight under Jorgen while the engineers, led by Rodge, try to work out how a creature that teleports can be turned into a reliable hyperdrive. The obvious source of more slugs is the cavern system of Detritus itself, and FM finds herself drafted into hunting them: coaxing them out, learning what they eat and what frightens them, and discovering that the taynix are not all alike, with different varieties doing markedly different things. At the same time the politics of the planet close in. The National Assembly wants the slug program controlled and quiet, and FM, who has never accepted that a government should decide what its citizens are allowed to know, starts asking questions that make her unpopular with everyone senior to her.

The slug work becomes the most important project on Detritus and the most fragile. FM and Rodge spend their days together on it and become close in a way neither of them quite says out loud. Every advance makes the same problem sharper: the taynix are living creatures, they respond to being treated well and badly, and the Superiority's method of using them is not one anybody involved wants to copy. Meanwhile the strain on Jorgen grows, because he is a cytonic, a flightleader and the person the Assembly keeps summoning, and the three roles do not fit together. FM's disagreements with the Assembly harden from irritation into a genuine argument about who commands the DDF and who is entitled to the truth. And the Superiority has noticed that Detritus is no longer a sealed problem, which means the next attack will not be drones probing a shield.

A Superiority force moves against Detritus, and the DDF fights it with a capability it did not have a month earlier: ships that can hyperjump into a battle and out of it. The slug program, and the care taken over the slugs themselves, is what makes the difference, and humanity ends the fight mobile instead of besieged. The political argument is only half resolved; FM has pried open some of what the Assembly was withholding, Jorgen carries authority well beyond his rank, and who actually governs Detritus remains an open and worsening question. FM and Rodge stop pretending about each other. Alanik, no longer stranded now that hyperjumping is possible, leaves for ReDawn to warn her own people against signing themselves over to the Superiority, which gives the humans their first real prospect of an ally. Spensa is still gone and still unreachable, and the war has plainly stopped being something that can be fought over one planet.

The slug program works. Enough taynix are found, coaxed out and sorted by what they can actually do that the DDF can hyperjump ships rather than merely defend a fixed position, and when a Superiority force arrives to close Detritus down, that mobility is what carries the engagement. Humanity ends the story no longer trapped at the bottom of its own gravity well, with hyperdrives of its own and a fleet that can appear where it is not expected. FM's argument about who is entitled to know things is only partly won: she has forced open a little of what the National Assembly was holding back, and Jorgen has taken on more responsibility than his rank warrants, but the question of who actually governs Detritus is left unsettled and will get worse. FM and Rodge, who spent the whole crisis working together, admit what has been obvious to everyone else. Alanik, no longer stranded now that hyperjumping is possible, leaves for ReDawn to warn her own people and to try to stop them signing themselves over to the Superiority, and the humans have their first real prospect of an ally against Winzik. Spensa is still gone, still unreachable, and the war is now something the DDF will have to fight beyond its own sky.