Warning: This post contains major spoilers for Glass, Unbreakable, and Split.
The connection between 2000’s Unbreakable, which starred Bruce Willis as David Dunn, a security guard and lone survivor of a destructive train crash who realizes that he might actually be a superhero, and Split, was a moment more than 15 years in the making. According to The Hollywood Reporter, the character of Kevin Wendell Crumb (James McAvoy), diagnosed with an extreme case of dissociative identity disorder (DID) that leaves him with 24 distinct personalities, was in the original script for Unbreakable, but was cut so the movie would focus solely on David’s origin story. Shyamalan then decided to devote an entire other film to Kevin's arc, hence Split.
The two films merge in Split’s final scene, when a news story recapping Kevin’s escape after kidnapping three teenage girls — only one of whom survived — is shown in a bar where David happens to be sitting.
So, where does Glass come in?
Like most Shyamalan movies, Unbreakable ended with a twist. In the final moments, David learns that Elijah Price (Samuel L. Jackson), the comic-book expert responsible for making him realize his true potential, actually caused the accident on Eastrail 177, as well as other attacks aimed at forcing superheroes to reveal their true selves. Horrified, he helps the police arrest Price, who suffers from a rare condition that causes his bones to break easily — like glass. In the end, Elijah, who now goes by the nickname “Mr. Glass,” is committed to a mental asylum for the criminally insane.
Unlike, the first two films, which focused on individuals, Glass brings all three superbeings together. The movie opens with David roaming the streets hunting The Horde, who have kidnapped another group of teenage girls. When he comes across one of Kevin’s personalities, Hedwig, he bumps into him, and his ability to sense people’s crimes gives him a clue as to where the girls are being held. David frees them, but encounters The Beast, Kevin’s most destructive personality that imbues him with superhuman strength. As the two fight it out, they’re surprised by a team of cops lead by Dr. Ellie Staple (Sarah Paulson), a psychiatrist who studies people who believe they are comic book characters. David and Kevin are brought to Raven Hill Psychiatric Center — where Elijah is still being held — for evaluation.
The rest of the film follows Staple’s attempts to get Kevin, David, and Elijah, to believe that they are just normal men with frontal lobe issues causing their delusions. But as Glass ramps up to its final confrontation, we learn that’s not the case. This is Shyama-land after all, and things can’t end as easily as we think.
Elijah recruits The Beast as his fellow villain, telling him that it’s their mission to show the world that there are really superheros out there. He also lets David, held in cell barred with a steel door, in on the plan. If David can get through the door, he can stop them — but that would also prove he’s no mere human.
It all comes to a head in the hospital parking lot. David confronts The Beast as Elijah eggs him on, and for a while, it looks like the two might kill each other. That is, until Joseph Dunn (Spencer Treat Clark), David’s son, shows up with some life-changing information.
As we learned in Split, Kevin’s DID was exacerbated by his father’s abandonment. Clarence Wendell Crumb boarded a train one day and never came home, leaving young Kevin at the mercy of his abusive mother. The Beast emerged as a way to counter that violence and keep Kevin safe.
But Clarence didn’t just board any train. Joseph reveals that he died on Eastrail 177, the same train wreck David survived. So, in essence, David and Kevin are both victims of Mr. Glass. (Some critics have been comparing this moment to the one in Batman vs. Superman, in which the two stop fighting because both their mothers are named Martha. It’s all VERY convenient.)
This new development causes Kevin to turn on Elijah, whose bones can’t resist the assault. He falls to the ground, mortally injured. It’s then that a SWAT team, summoned by Dr. Staple, arrives into the mix. They shoot Kevin, who had finally reemerged as a dominant personality after connecting with Casey Cook (Anya Taylor-Joy), his victim-turned-friend from Split, and force David’s head into a puddle of water to restrain him. (We learned in Unbreakable that water is his weakness).
As David struggles, we catch a glimpse of a tiny clover tattoo on Dr. Staple’s arm, one that also appears on his assailant. “Did I almost convince you you were an ordinary man?” she purrs. By touching David, she reveals her true nature: Staple is part of an secret society whose mission it is to stop the emergence of superheroes. “There just can’t be gods among us,” she explains.
In the end, David, Kevin, and Elijah all die, and it looks like their exploits will never be known. Until — the next twist!
It turns out that Elijah coded the security cameras at the hospital to livestream the fight between David and The Beast on a private website, the link of which appears in Joseph and Casey’s inboxes shortly after the incident. The last scene shows them, along with Elijah’s mother (Charlayne Woodard) sitting in Philadelphia’s 30th Street station — where David had his first initial Big Superhero Moment — as phone alerts go off. Superheroes are real. And now the world knows.