Undoubtedly many of you probably heard that Split, the latest offering from M. Night Shyamalan had its world premiere at Fantastic Fest in Austin, TX earlier this week. It was the festival’s only secret screening of the year, so no one (not even the staff) knew what we were going to be watching. Rather than get a review out immediately following the screening, I wanted to let the film stew for a while so I could fully process it. Overall Split is a step in the right direction for Shyamalan and lets him shine as a director, but it isn’t without its flaws.

Not many directors have inspired controversy as much as M. Night Shyamalan. After his success with The Sixth Sense and Unbreakable, the director found himself in a creative rut. As his budgets got bigger, his films got worse. Last year’s The Visit (my review) saw Shyamalan working with a noticeably smaller budget than usual ($5 million), and it was a return to the form for the director. With Split Shyamalan is working on a similar (but as yet undisclosed) budget that helps rein him in from his self-indulgent tendencies. This doesn’t mean the film is without its flaws, but it’s a solid film with one astounding performance from James McAvoy.

Beginning at the end of a birthday party, Split sees teenage girls Casey (Any Taylor-Joy, The Witch, Morgan), Claire (Haley Lu Richardson, The Bronze) and Marcia (Jessica Sula, Honeytrap) abducted by Kevin (McAvoy, Wanted, the X-Men prequels), a man living with dissociative identity disorder. A childhood trauma fractured Kevin’s psyche into 23 different personalities, or alters, and one of them has a fetish for doing lewd things to young girls. Helping Kevin live with his disorder is Dr. Karen Fletcher (Betty Buckley, Carrie, The Happening), a psychiatrist who attempts to help integrate him into society.

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Right from the start Split grabs hold of you and doesn’t let go. The opening sequence is incredibly creepy and while the film isn’t necessarily scary (IMDb lists it as a horror film but it most definitely is not), it is thrilling. It has a tendency to get bogged down in over-explaining things (more on that in a bit), but the film is exciting from start to finish. There are just a couple of issues with the screenplay that prevent Split from being truly great.

Earlier this year some viewers were critical of Lights Out due to the implications of the film’s ending and what it said about depression. Split plays like a cross between Identity and Red Dragon (three of the alters are awaiting the arrival of a 24th alter, known as “The Beast”), making some bold statements about mental illness that may generate similar criticisms. They’re unwarranted though, as Shyamalan does give Split a captivating perspective to the disorder. It may not fully hold up under scrutiny, but boy does it make for some terrific entertainment.

As a director, Shyamalan has rarely been better. His directing style has always been playful, and he continues that streak here. The aforementioned low budget allows him to be more experimental with his shots and filming style, making for an entertaining viewing experience. Surprisingly, he shows his hand early on in the film, making the narrative more straightforward than one would expect. This is jarring at first, but it lets him to have more fun with viewers who might be expecting a more twist-reliant narrative.

Kudos must be given to McAvoy, who (pardon the cliché expression) steals the show. He’s up there with Tatiana Maslany in terms of his ability to fall into a character. The mannerisms, speech patterns and little ticks he gives each of his alters are immediately noticeable. You almost wish that more time was spent exploring all 23 of the alters (only about 6 are given any screen time), but what Shyamalan and McAvoy have given us is fascinating to watch. From the Norma Bates-ish Patricia to the Francis Dollarhyde-y Dennis, McAvoy transforms into these characters. There are a few moments where the alters converse with each other through Kevin that sends chills up the spine. The entire film could have been McAvoy alone in a room talking to himself and it probably would have been great.

Actress Anya Taylor-Joy does what she can with an underwritten role, but she isn’t given enough material to truly shine. Shyamalan tries to shoehorn in a disturbing backstory involving domestic abuse, adding a certain amount of ickiness to the film, but it feels like it belongs in another movie. Richardson and Sula don’t fare nearly as well as Taylor-Joy. The actresses are fine in their respective roles, but their inclusion in the film seems like an afterthought. One could surmise that Split would have worked better had it been set solely in the room where the girls are kept, with McAvoy and Taylor-Joy being the only two leads. This would have made for a very different film of course, but it would have provided more opportunities for suspense and mystery.

Buckley, while a wonderful actress, is severely overused. Her inclusion gives Shyamalan a reason to pad the runtime to almost two hours (though to the film’s credit, it does not feel that long). Her character exists merely to explain the plot in detail to the audience, and it is borderline insulting. Imagine if the psychiatrist from Hitchcock’s Psycho sporadically popped up throughout that film and began diagnosing Norman. That is essentially Buckley’s purpose in Split, and it dilutes much of the film’s suspense. This would be somewhat forgivable if her Dr. Fletcher wasn’t the worst psychiatrist in the world, but she is. Buying into the fact that she continuously refuses to called the police after a certain point requires a significant suspension of disbelief that the movie doesn’t earn. It is the only major misstep in Shyamalan’s script, but it nearly kills the film.

Lastly (and I will try to keep this as spoiler free as possible), one can’t discuss the film without mentioning its final minute. Much fuss has already been made about it and while I wouldn’t necessarily call it a twist, it does severely alter the way the film will be viewed on subsequent viewings. This last-minute revelation is the reason I wanted to wait a day or so before reviewing Split. The contents of the film’s closing moments are so awesome that you walk out on a sort of high that almost makes you forget all of the flaws that came before it. Almost. Still, it’s a fun trick for Shyamalan to pull out of his hat and it pays off in spades. I implore you to avoid any social media mentions about the film, as having Split spoiled for you would be a tragedy.

Even though Split has its flaws, there is still plenty here to recommend. Shyamalan is at the top of his directing game, but he still hasn’t learned to fine-tune his writing. Like many of his films, it will no doubt split (sorry) audiences, but McAvoy’s performance alone earns the film a full recommendation. He is a marvel to behold.

Split will open in U.S. theaters nationwide on January 20th, 2017.