When Peter leads two Tinkerers to his family's inn in Stargazers Valley, he imagines they're like other astromancers, researchers from the Imperial College who study starstuff. The valley is a special place, where the magical aurora called the Skeins appear in the sky and starstuff falls in their wake, as thin and wispy as fluff from a seed pod. But starstuff is powerful, and astromancers are the only people allowed to handle it--a law enforced by the strict and stealthy Outbounder Task Force. When Peter discovers the Tinkerers have used starstuff to invent an incredible not-a-clock that can turn back time for a few minutes, he realizes it's his chance to undo his mistakes: if he can go back and put away his new boots, he doesn't need to add their destruction by falcons to his list of ten worst mistakes (#7: stepping on a star-eating newt). But while using the not-a-clock is easy, stopping using it is hard. And maybe not everything that feels like a mistake at the time actually is. Family, friendship, and budding self-confidence are at the heart of Caroline Carlson's stellar fantasy.