After the events of X-Men: Apocalypse, the X-Men are national heroes, known for tackling several risky missions. On one such mission Jean Grey is hit by the deadly radiation of a solar flare. She attains her maximum power and becomes the Phoenix. But before long Jean gains powers that corrupt her to the core and turns into the Dark Phoenix. The X-Men have little time to decide if the life of a teammate, a woman they cherish, is worth more than the existence of the entire world and its people.