James McAvoy always struck me as an entertaining performer, a charming and charismatic rogue who doesn't look out of place in either a period drama or a comic-book property. Prior to Split, I would have stopped short at calling McAvoy "versatile," but M. Night Shyamalan's bare-bones thriller changes the game.

The main reason anyone should check out Split is to marvel at McAvoy's breathtaking performance. He plays Kevin, an unassuming Philadelphia man suffering from Dissociative Identity Disorder, and the plot device allows McAvoy the opportunity to transition between at least seven different characters by slightly changing a facial expression, altering his clothing or, miraculously, affecting a new accent for each person. One minute, McAvoy is lisping, with wide eyes and a youthful exuberance, because he's playing Hedwig -- a mischievous 9-year-old "boy." The next minute, McAvoy has the tut-tut-tut discipline of a British nanny because he thinks he is "Patricia." Kevin has 23 different personalities, and is developing a 24th, and McAvoy, astonishingly, has interesting ways to visualize all of them.

What's even more astonishing is that this whirlwind performance props up an M. Night Shyamalan thriller, because regardless of what you think of the man as a director and storyteller, he isn't widely recognized for bringing multi-faceted performances out of his leads. Every actor from Mel Gibson (Signs) and Bruce Willis (Unbreakable, The Sixth Sense) to Joaquin Phoenix (The Village) have turned in subdued, low-wattage turns under the guidance of Shyamalan, who specializes in slow-burn horror. You do tend to expect the unexpected in his movies. I just didn't know that McAvoy would be the main surprise.

Split is a slow-burn horror, though, centered around Kevin's heinous act of kidnapping three innocent teenage girls, which one of his personalities -- Dennis -- believes they need for a ritualistic sacrifice. He keeps the girls in a dingy basement, and they deal with his personalities as we piece together a series of mysteries to figure out what is in store for them.

Shyamalan develops two concurrent storylines that cleverly explain to the audience the depth of Kevin's disorder, and the plight of the kidnapped women. In one, Dr. Karen Fletcher (Betty Buckley) researches Kevin as a groundbreaking case study, explaining to her colleagues that the different identities Kevin possesses come with various physical abilities -- and possibly even supernatural abilities. For example, if one of the personalities whole-heartedly believes that they are a Russian bodybuilder, then Kevin might be able to bench press 450 lbs., despite the fact that he's built like James McAvoy.

In the second, and far more disturbing, subplot, Shyamalan fills in the backstory of kidnapping victim Casey (Anya Taylor Joy), a quiet and ostracized teenager who suffered horrific abuse at the hands of a loved one... an experience that might have properly prepared her to deal with Kevin and his unpredictability.

Casey's subplot disturbed me, probably because Anya Taylor-Joy, who was so affecting in The Witch, sells the vacant stare that comes with detached abuse so well. I could feel Casey's pain through the screen, and the more Split dwelt on it, the more I begged it to move on to another story. To any other story. You might have the same reaction. You might not.

Thankfully, when Split does move on, it usually lands on McAvoy, who -- as I mentioned -- is having a complete blast exploring the various aspects of Kevin's dangerous personalities. Ultimately, the kidnapping drama at the heart of Split isn't hefty enough to sustain the film's run time, and the resolution that it builds to -- the "releasing" of Kevin's newest personality -- isn't quite worth the time it takes to get to it. You'll never be bored with Split, as McAvoy and the general tension of the situation more than hold your interest. (Heck, I'd argue that McAvoy needed more screen time to show off a few of Kevin's personalities that never made it into the spotlight.) But trying to deduce where Kevin is keeping his victims was a more engaging mystery than unraveling how they were going to inevitably escape.

Because this is M. Night Shyamalan, there is a final twist. And it's a great one. You're not going to hear it here. I truly hope you don't hear it anywhere before you see it in the theater. But because of our day and age, and the inability to keep any secret under lock and key, I suggest that if you are a Shyamalan fan, and you have an interest in seeing Split, go as early as possible, and enjoy the final scenes unscathed. They, alone, are worth the price of admission.

Sean O'Connell
Managing Editor

Sean O’Connell is a journalist and CinemaBlend’s Managing Editor. Sean created ReelBlend, which he proudly cohosts with Jake Hamilton and Kevin McCarthy. And he's the author of RELEASE THE SNYDER CUT, the Spider-Man history book WITH GREAT POWER, and an upcoming book about Bruce Willis.