During a rescue mission in space, Jean Grey (Sophie Turner) is nearly killed when she is hit by a mysterious cosmic force. Once she returns home, she begins to develop incredibly powerful psionic abilities that corrupt her and threaten to destroy the universe, leading the X-Men to decide whether her life is worth more than all other living beings.

Wrestling with this entity inside her, Jean unleashes her powers in ways she can neither comprehend nor contain. With Jean spiraling out of control, and hurting the ones she loves most, she begins to unravel the very fabric that holds the X-Men together. Now, with this family falling apart, they must find a way to unite — not only to save Jean’s soul, but to save the planet from aliens who want to weaponize this force and rule the galaxy.