M. Night Shyamalan's Glass: 7 Plot Predictions

At the end of Unbreakable, we're informed (via onscreen text) that Elijah was taken to an institution for the criminally insane, after David Dunn led the authorities to discover evidence of Elijah's many acts of terrorism.

At the end of Split, we learn that it's been fifteen years since Elijah was put away.

So, if Glass picks up shortly after that movie, Elijah will still be incarcerated - presumably, fifteen years is too short a time for a crazy mass-murder to be released back onto the streets. Plus, the woman in the diner can't remember his name - he's evidently faded from the public consciousness, indicating that he's still deep into his sentence.

So, he's going to need to get out at some point. After all, his name's in the title of the movie, and it wouldn't be much of a compelling story to just watch him eat prison food and be consistently subjected to interviews by condescending psychiatrists.

But how does he get out? Does he escape, or leave legitimately? We think it's the former. He'll probably be locked away for life given the fact he murdered dozens of people, so perhaps a breakout is the only answer.

And this is where Kevin comes in. We could get a cool horror-infused scene where The Beast stalks and kills the staff of the criminal institution at night (like the scene where he chases Casey in Split, with the character crawling along the roof and hiding in the shadows), before springing Elijah from captivity.

Kevin and Elijah would then be on the run, which gives David a reason to pursue his old acquaintance, bringing him back into the game.