Coll belongs to Wolf. He lives with his crew on a Construct, a huge technological "creature" driven by the crew's combined willpower.

Together they roam their world, fighting other Constructs and absorbing them into their own. But when a new and dangerous Construct attacks them, Coll is thrown clear from Wolf and left behind. Now he must survive life on ground and get back to his crew.

He is helped by Rieka, a "Tock" who makes the Constructs work. She promises Coll a way to return, but can she be trusted? And what is she really trying to do...?When Coll uncovers the truth, it destroys everything he thought he knew about Wolf, the world they live in, and even himself. In a world full of danger, and suddenly without meaning, can he find a way back?