For the first few minutes of “Split,” I was beginning to reconsider M. Night Shyamalan as a filmmaker. I’ve never particularly been a fan. It wasn’t just “The Village” and “The Happening” that turned me off; I didn’t even like his so-called ‘best’ films “The Sixth Sense” and “Unbreakable.”

But in the opening moments of “Split,” he establishes three characters (two best friends, one weird girl no one likes) and has James McAvoy get into their car and spray them unconscious, then has the girls wake up in a little room with three beds and an ensuite.

I was hooked. He didn’t faff, he just jumped right in. But I very quickly re-reconsidered when Betty Buckley came in to bore me to death with all that trailer fodder dialogue about how “we see people with multiple personalities as less,” and how they’re the next stage of human evolution which work better over clips of McAvoy running shirtless on subway tracks. That’s when I realised “Split” works better as a trailer than a Film, and my brief love affair with M. Night Shyamalan reached an end.

Another disappointing execution of a brilliant concept by Shyamalan

Shyamalan’s not a good storyteller. He has really great premises and then makes one fatal mistake in his execution that kills the whole thing.

So, he has an idea like a mysterious virus making people commit suicide, and then kills it by making plants responsible. Or he has an idea like an old-timey village haunted by creatures and then kills it by showing up literally in the film to reveal it’s all a big present-day scam. Or he has an idea like a guy with dissociative identity disorder kidnaps three girls but then kills it by making the guy turn into a monster.

And so goes “Split.”

Aside from the fact that the film perpetuates stereotypes about mentally disabled people that they are automatically dangerous or scary because they have multiple personalities, “Split” has serious structural problems. There’s too much time spent on the boring therapist and not enough time spent with the girls in captivity, because that’s what’s really interesting in the film.

By jumping back and forth between these two worlds, Shyamalan is trying to do what Hitchcock does in “Psycho,” but where Hitchcock masterfully creates tension and suspense, Shyamalan creates annoyance that we’re hearing what some old kook thinks about DID instead of being scared.

And the climax, when Shyamalan finally gets there (stop laughing), is far too disjointed. It’s like Shyamalan couldn’t decide how it should end so he just kept writing the first thing that came to mind and then what he finally settled on is just stupid. Like all of Shyamalan’s films, “Split” ends with a twist (a few, actually), but one can be called from the get-go and it involves the shoehorned-in flashbacks that we’re subjected to throughout, and one only serves to link it to one of Shyamalan’s earlier films, which is pointless.

However, James McAvoy’s performance is unbelievable

The saving grace of “Split” is James McAvoy’s acting. He deftly switches from one personality to another, just with a shift of mannerisms or the way he moves his chin or inflections in his voice, and if that’s not impressive enough, he even convincingly plays one personality pretending to be another at one point, and the whole time you’re watching him work, you genuinely feel like you’re watching different actors. It’s incredible. It’s so good that it could even be seen as too good. For example, when McAvoy is Hedwig, the nine-year-old personality with a lisp, he plays it so well that you actually believe you’re watching a nine-year-old boy trying to impress a girl and showing off all the cool things in his room, so it’s just cute, it’s not creepy like it would’ve been in the hands of a lesser actor.

You actually forget you’re watching a grown man, which is haunting in itself.

Split” isn't a great film or even a good film. It’s a mediocre film with an unbelievably great lead performance, but it’s worth watching just for that.