Having escape from the Hellfire Club, Jean Grey finally gives into the dark side of her soul awakened by Mastermind, becoming the Dark Phoenix and destroying the X-Men's escape craft over Central Park. Miraculously, the X-Men survive the explosion and with quick thinking manage to make it safely to ground with only minor injuries. Their attempts to talk Jean out of attacking them fails and she easily trounces the team with her cosmic level abilities.
While not far away at the Hellfire Club, the authorities are investigating what patrons there believe was an attack by the X-Men. After seeing his colleague Henry Leland wheeled into an ambulance, Sebastian Shaw confronts US Sentator Robert Kelly, a guest at the party that nught. He recommends to Kelly using his government connections to restart the Sentinel program so that they can hunt down dangerous mutants as part of his secret scheme to vilify and destroy the X-Men. Before the two men can discuss things further, Shaw is shocked to see a giant Phoenix effect fill the sky. Shaw is not the only one, as Dark Phoenix uses her powers to fly away from Earth her abilities are picked up by Mr. Fantastic's scientific equipment, Spider-Man's spider-sense, Dr. Strange's mystical senses, and the Silver Surfer's cosmic senses. As Jean departs, an Avengers Quinjet lands in Central Park containing the Beast who has come to the aid of his former comrades in the X-Men. He finds them beaten but alive and agrees to fly them back to the X-Mansion in Salem Center. While in New Mexico, Professor X has a video call with Moira MacTaggert on Muir Island where they both compare notes and realize that their greatest fear, that Jean has lost control of her new powers, has finally become a nightmarish reality.
While in space, Dark Phoenix loops around the sun and uses it's gravity to sling shot her out to a warp gate not far outside of Earth's solar system. This sends her to the D'Bari system, which is part of the Shi'ar empire. She then feasts on the solar system's star, causing it to go nova and obliterate all the living creautres on the planet D'Bari. This is witnessed by a Shi'ar flagship that goes in to investigate. While on the Shi'ar throneworld, Empress Lilandra is awoken to the news of the destruction and witnesses the destruction of the flagship at Phoenix's hands. Lilandra grimly considers that they must deal with this threat no matter the cost.
On Earth, the X-Men have returned to their headquarters and wonder what they will do next. Scott, who still has his telepathic rapport with Jean witnesses the entire genocide through his minds eye and warns his fellow X-Men that Jean is returning to Earth, and she's hungry.