Spider-Man: Brand New Day is now playing in theaters worldwide, with Tom Holland swinging up against a mysterious villain with an even more secretive backstory. Director Destin Daniel Cretton has delivered another spectacular Spider-Man installment to the MCU, having taken the baton from Jon Watts, who directed the Home trilogy.
Part of Cretton's new success is zeroing in on Peter Parker's psyche and what it means to be Spider-Man in a world where everyone has forgotten who he truly is. Adding to that narrow focus is a complex foe, whose own origins collide with Peter in a way many fans never expected.
Warning - The rest of this article contains major spoilers for Spider-Man: Brand New Day
The cat is out of the bag: Sadie Sink is officially the MCU's Jean Grey. After a long press run of having to deny and dodge questions about who she was playing, Spider-Man: Brand New Day has confirmed her identity as the mutant Jean Grey, without even giving her a secondary alias or trying to tell audiences she's playing anymore besides the eventual X-Man.
During Brand New Day, Spider-Man realizes that it's Jean who's able to mind-jump from person to person, as long as they're within 33 feet, basically becoming the focal point of villainy throughout the entire film.
During the events of Brand New Day, Jean attacks Spider-Man while inside the mind of Hulk, Scorpion, and The Hand. She even takes over MJ's consciousness, leading Peter to believe his ex-girlfriend actually remembered who he was (news flash: she does not).
Despite the heinous acts of Jean throughout the film, which are sure to cause some divisive fan reactions, she does conclude the film as a hero, or at least a mutant with a brighter future, who needs more mentorship; maybe a wise professor could help her one day.
Sink playing Jean was one of Marvel's worst-kept secrets, including a recent San Diego Comic-Con tease from Ryan Reynolds' Deadpool, but her origin story came as a major shock in theaters.
In a flashback sequence, audiences learned of Jean's older sister Sara, who is the entire reason Jean is currently trying to infiltrate the Department of Damage Control, with whom Spider-Man has aligned himself to start the film.
In Marvel Comics, Sara Grey is a minor supporting character, introduced in 1966 as Jean's older sister, and has appeared only sporadically since. She didn't actually appear on the page until 1980's X-Men #136, during the Dark Phoenix Saga, when Jean revealed her mutant identity to the family.
Sara was later married and had children, but vanished after she spoke at a mutant-rights rally in the late 1980s, and it was later confirmed (in X-Men #36 in 1994) that she'd been murdered by anti-mutant extremists, with her body being absorbed by the Phalanx hive-mind.
Most recently, Marvel resurrected Sara under mysterious circumstances in 2025's Phoenix series, giving the long-dead character another shot at relevancy.
Her interpretation in the MCU is a bit different; while she's still only playing a small role in the story, it's revealed that she basically has the exact same telepathic powers as Jean. In fact, Sara is the one initially trying to train Jean, showing her how to hop from person to person until you reach your target.
During the Brand New Day sequence, Sara is taken away swiftly by the DODC, leaving Jean stranded and alone. Then it all ties together, explaining to viewers the motivation behind Jean's villainous actions throughout the movie and her deep hatred for the DODC and its leader, Bill Metzger (Tramell Tillman).
Spider-Man learns earlier in the movie that Jean is looking for the mysterious "V-Max," which no one seems to understand what that even means. It's not until later, when the DODC is experimenting on Jean, as they previously had done to Sara, that V-Max was nothing but the letters she saw on the air conditioning unit before she died. So both on screen and on the page, Sara is destined not to be alive for a prolonged time, effectively just being part of Jean's larger story.
Jean Grey's MCU Introduction Explained
At long last, the MCU has introduced a new star to take on an iconic X-Men role. Previously, Marvel Studios had only made Ms. Marvel a mutant, historically an Inhuman, and leaned heavily into past X-Men eras, like Hugh Jackman's Wolverine and the return of James Marsden, Patrick Stewart, Ian McKellan, and more in Avengers: Doomsday.
In Spider-Man: Brand New Day, Jean Grey receives an entirely fresh origin story, including a dream-like memory, which puts Sink in a role with Marisa Tomei's Aunt May, receiving the same advice Peter once did (presumably during the time between Spider-Man: Homecoming and Avengers: Infinity War).
Searching and grieving for her sister Sara is what kicks off the Jean Grey story, but being saved by Spider-Man, emotionally and physically, is what will set the course for her to become a true hero in the MCU one day. Her story closes in hopeful isolation, but nothing is further revealed of her original universe, if she's even supposed to be from any reality other than Earth-616.
Sadie Sink's Jean Grey is expected to return in Avengers: Secret Wars on December 17, 2027, and later be a main part of the (expected) 2028 X-Men film, directed by Jake Schreier.
