• James McAvoy as Kevin Wendell Crumb / The Horde: A former Philadelphia Zoo employee with 23 different personalities whose body chemistry changes with each personality, resulting in a 24th personality known as "The Beast." Aside from The Beast, Kevin's personalities consist of Jade (a teenage girl), Orwell (an introverted man), Barry (the original dominant personality), Patricia (an orderly woman), Hedwig (a nine-year-old boy), Mary Reynolds, Dennis (a perverted man), Norma, B.T, Mr. Pritchard, Jelin, and Samuel. Crumb was previously introduced in Split.
• Bruce Willis as David Dunn / The Overseer: A security guard who possesses superhuman strength, stamina, and invulnerability as well as an extrasensory ability to see the crimes people have committed by touching them. In the film, Dunn goes by a new alias named "The Overseer."[12] Dunn was previously introduced in Unbreakable.
• Samuel L. Jackson as Elijah Price / Mr. Glass: A highly intelligent mass murderer and comic book theorist with Type I osteogenesis imperfecta who was institutionalized after Dunn discovered the extent of his crimes. Price was previously introduced in Unbreakable.
• Sarah Paulson as Dr. Ellie Staple: A psychiatrist specializing in delusions of grandeur who treats patients convinced they are superhuman beings.
• Anya Taylor-Joy as Casey Cooke: A teenage girl with a history of self-harm who was kidnapped by one of Kevin's personalities as a potential sacrifice to "The Beast", but managed to survive.
• Spencer Treat Clark as Joseph Dunn: David's son who has believed in his father's abilities since he was a child and sees him as a real-life superhero. He also has superhuman abilities like his father.
• Charlayne Woodard as Mrs. Price: Elijah's mother who took great care of her son and always told him he was special no matter what others said.
• Adam David Thompson as Daryl.
• Luke Kirby as Pierce.

David Dunn (Bruce Willis) works with his son in protecting people from criminals using their superhuman powers. He learns from his son that Kevin Wendell Crumb (James McAvoy) has a group of cheerleaders held up in a warehouse and David goes there to free them. When he gets there, he engages in battle with "The Beast" and the fight spills out to the streets. The cops are called and they are both eventually captured and sent to a mental institute where Elijah Price (Samuel L. Jackson) happens to be at.

Dr. Ellie Staple (Sarah Paulson) is the head doctor there who works with patients who claims they have special powers in suppressing those thoughts. She works with them in persuading them that there is no such thing as special powers and they are dealing with a mental illness. Meanwhile, Elijah is secretly working with Kevin in unleashing The Beast and exposing the world to the existence of superheroes. With the help of The Beast, Elijah escapes and soon is pursued by David, who battles The Beast again on city streets. Ellie arrives with military men and explains that she has spent majority of her career preventing other superheroes from exposing themselves to the world. The military men are in the same secret society Ellie works with. They capture David and kill him by drowning him in a puddle. Elijah is killed by Kevin once it comes out that the train crash Elijah provoked to find David also killed Kevin's father, who was on the same train. (This made his mother mistreat Kevin, torturing him, leading to the creation of Kevin's personalities including the horde to protect him.) Eventually, Kevin is also killed by the military men.

Meanwhile, the cameras inside the mental facility have been secretly hacked by mastermind Elijah and the footage is released to the world, showing them that superheroes in fact do exist. Ellie then realizes in shock that her and the secret anti-superhuman society's plans are ruined now since everything she fought hard to hide has been released to the public.

Glass movie review: A convoluted superhero filmBy:The Indian Express - 18 January,2019

Glass movie review: M Night Shyamalan’s Avengers-style universe comes crashing downBy:Hindustan Times - 18 January,2019

A Quick Recap of Everything You Need to Know Before Seeing GlassBy:Gizmodo - 17 January,2019

Glass Review: Shyamalan's Superhero Trilogy Finale is One Weird BeastBy:Screen Rant - 16 January,2019

Film Review: Glass Marks a New Low for M. Night ShyamalanBy:Consequence of Sound - 16 January,2019

M. Night Shyamalan's Biggest Twist? Coming Full CircleBy:New York Times - 15 January,2019

Film Review: M. Night Shyamalan's 'Glass'By:Variety - 09 January,2019

Review: 'Glass' Is M. Night Shyamalan's Most Disappointing MovieBy:Forbes - 09 January,2019