At home in his lair: James McAvoy as Kevin in “Split'” Credit: Universal Pictures

For a thriller, there sure was a lot of laughter in the preview audience of M. Night Shyamalan’s Split. It wasn’t just nervous laughter either, the kind that’s necessary in a movie to release the tension for a moment, till the next nosedive into terror. No, not that kind of laughter, as this tittering was over the silliness of the plot, the mumbo jumboness of the dialogue, and the finally revealed great big secret of the dark, suffocating location. Kevin (James McAvoy), or Hedwig, or Orwell, or Samuel, or Jade, or Dennis, or Barry, or Lady Patricia, etc., not only keeps us guessing but keeps us laughing.

Thus we are essentially laughing over mental illness. Kevin’s dissociative identity disorder (DID) as he channels his multiple personalties is a real phenomenon identified by the American Psychiatric Association. But so much for our supposed growing awareness of mental health issues in the public sphere. Apparently such personality disorders are still ripe for exploitation, manipulation and mass entertainment. What’s next? How about a yock-fest on PTSD and all those quirky manifestations? It’s obvious already that OCD is a great source of media hilarity, so it’s not surprising that split personalities with all their cinematic possibilities continue to provide fodder for amusement. This is a field thoroughly plowed by previous Three Faces of Eve; Sybil; Fight Club; Me, Myself and Irene, and plenty of others.

James McAvoy Split Credit: Universal Pictures

The best thing about this film is the showcase it provides James McAvoy (Atonement, X-Men, Filth) as he manages to convey if not all 23 of the personalities, then certainly a good number of them. He has long been an overlooked and underrated actor. Surely this single role will let casting directors see the range he’s capable of delivering, whether a lispy, whispery child, a fey costume designer, a stern mother figure in severe pencil skirt and black stilettos, even a roid-raged, bone-popping, blood-sucking beast.

Unfortunately when you are so divided and compromised by this many people in your head, there’s not much time in a two-hour movie for character development. We jump and shift rather abruptly among his personalities, making us wonder how he possibly has time to change into the appropriate clothes from his vast closet, or how he manages to create all the art work decorating his quarters, or when is it he videotapes and catalogs his various personas speaking directly to the computer camera. And how does he manage to elude detection in his underground lair for so long? Some questions are best left unasked.

That said, ironically, we know far more about the multiple characters in his mind than we know about the three victims of his violence. Of course the victims are nubile teenage girls, of course the victims are clueless and self absorbed, of course the victims misunderstand their persecutor and their fate till it’s too late. Two of the victims are cyphers, little more than disposable adolescents, but still girls with taut abdomens which we see a lot of as they, understandably, are forced to remove their clothes down to their panties and lacy bras. The third victim does have a past, but keeps her clothes on, and we learn her history through flashbacks, all of which propel her as the opponent most likely to give the bad guy his comeuppance. Indeed, Anya Taylor-Joy (The Witch) as the silent, staring Casey sets herself apart, literally and figuratively, from the others. As we learn “the broken are the more evolved,” then Casey is the one girl who’s destined to best understand Kevin’s divisions and primed to deliver the film’s bloody resolution.

One strong woman in the film is Dr. Fletcher, played by the inestimable Betty Buckley, better known for her work in London and New York musical theatre. But here she plays Kevin’s psychiatrist who keeps a running commentary with the audience, via a Skype video conference with her colleagues, about such personality disorders. It’s the equivalent of voiceovers and it’s really just talk, talk, talk. To know Kevin, et al. so well, she’s remarkably uninformed about his true nature. She even observes “we are what we believe we are,” but ultimately, she’s a disposable victim also.

This film is one more in a long line of Shyamalan’s take on contemporary horror, terrorizing us with The Sixth Sense, Signs, Unbreakable, among many others, and now Split. We go to his movies expecting to be thrilled. It’s a sad letdown that Shyamalan resorts to the supernatural to bring the film to a clunky close. This time it’s not M. Night Shyamalan who thrills us but James McAvoy.