It took M. Night Shyamalan nearly two decades to assemble the heroes and villains for his comic book thesis movie, Glass. When he finally got the interest and budget to make the movie, he for some reason decided to keep those super-people locked up and sedated for the better part of two acts, with doctors and nurses orbiting around them and delivering exposition to the few people that still care about these outcasts.
The sidelining of the super-characters — David Dunn (Bruce Willis), Kevin Crumb (James McAvoy), and Elijah Price (Samuel L. Jackson) — wasn't particularly problematic, because after featuring in their own movies, none of them were particularly interesting. The mistake Shyamalan made was in deciding to focus much of the conversation and action on those characters anyway, making for a dialogue-heavy, philosophical movie that arrived about a decade too late. And in making Glass an explainer piece, he ignored the best and most interesting characters: the aforementioned trio of people who are for some reason still invested in these toxic, super-powered maniacs.
**Spoiler Alert: There are spoilers for Glass below**
The healthiest relationship in the Unbreakable-Split-Glass ad-hoc trilogy is between David Dunn and his son Joseph (Spencer Treat Clark). Sure, Joseph points a gun at his dad at one point in Unbreakable, but he was a little kid then, and besides, he was ultimately right that a bullet wouldn't have hurt him much, anyway. By Glass, Joseph is working for his dad at his home security store and acting as his eyes and ears when David goes out on patrol in Philadelphia. His mother (and David's wife) died at some point over the last 20 years, so it's just the two of them, working in the store and serving as a petty crime-fighting team.
It's unclear what else Joseph has been doing with his life — he has some computer skills, but he's mostly just zooming in on Google Maps — but we do know that he's desperately and unhealthily attached to his father. We never see any friends or even co-workers, and there's no indication that he has a life outside the shop; he's well past when most people his age would have graduated from college and moved on to their own dreams and ambitions.
There's nothing wrong with not leaving one's neighborhood, but an exploration of this kid, who grew up with a very damaged quasi-superhero dad and lost his stabilizing mom along the way, would have been far more interesting than seeing Bruce Willis sit quietly in a jumpsuit for most of the movie.
Similarly, Elijah Price is catatonic through much of the film, yet there is his mother (Charlayne Woodard) still visiting him decades after learning about his long list of terrorist attacks. A mother's relationship with her criminal child is always interesting, and in this case, Mrs. Price is even more interesting due to the many years she spent caring for her brittle little Mr. Glass. What does knowing that you tended to a child's every need, only to see him become a madman terrorist, do to a person? How do they handle what must feel like overwhelming guilt and betrayal?
Woodard portrays a loyal mother who sticks by her child's side, and her interior life must be fascinating. Does she do so out of guilt? Does she resent her son? Would she ever just give up on him? We never find out, because she's as good as window dressing throughout.
The end of Split offers a glimpse of humanity inside of Kevin Crumb's many monstrous personas when he lets Casey Cook (Anya Taylor-Joy), one of the girls he kidnapped, out of his underground prison. He releases her because he senses that she is different and he feels some kinship with her, like some kind of reverse Stockholm syndrome. It's a relief for Casey, who we assume hightails it out of there and into some new lonely life, so it's a bit of a shock when we learn that she has stayed loyal to Kevin and visits him when he's locked up in the clink.
Obviously, the Stockholm syndrome has flipped, and she now suffers from a perverse sympathy with her one-time captor. Sure, he did let her go from the torture basement, but she saw him carry out unspeakably evil acts for days, killing two of her classmates and a psychiatrist who had treated him for years. Even if accidentally, Shyamalan created a fascinating character, and Glass would have been smart to explore someone who witnessed all that she witnessed and then still decided to return to Kevin's side.
One of the major criticisms of Glass is that very little happens in it. That could have been remedied by exploring what happened before it takes place.