As Jean Grey pushes her powers to the limit, shaking her and the rest of the X-Men to the core, one of the young X-Men breaks rank – and leaves to join the adult Cyclops and his revolutionary crew! And when Mastermind targets the young Jean, will history repeat itself? Plus: When the teens find themselves face-to-face with the Uncanny Avengers, young Cyclops meets the adult version of the brother he thought he’d never see again! They never warned us about this sort of thing in temporal mechanics class! Collecting: All-New X-Men 11-15