‘Split’ review: Enjoyable, clever one-up of ‘Psycho’

“Split,” a psychological thriller starring James McAvoy as a man with 23 personalities, is the latest from M. Night Shyamalan, a writer-director whose movies range so widely in quality that he also might have multiple personalities. Shyamalan has been the Hitchcockian mastermind who gave us “The Sixth Sense,” the creative comic-book geek behind “Unbreakable” and the dunderhead who stapled together “The Last Airbender.” The good news is that, for most of its nearly two-hour running time, “Split” is quite enjoyable, a clever one-up of “Psycho” with some interesting twists and several funny-creepy moments.

In its final 20 seconds, however, “Split” suffers a kind of psychotic break and does something so dumb, so exasperating — so Shyamalanian — that it nearly wrecks everything.

For the moment, let’s focus on the positive. “Split” makes the absolute most of its star, and vice versa. We first see McAvoy as Dennis, a stern handyman who kidnaps three teenagers: friendly Marcia (Jessica Sula), pampered Claire (Haley Lu Richardson) and the school outcast, Casey (Anya Taylor-Joy). Dennis soon gives way to matronly Patricia, outgoing Barry, 9-year-old Hedwig and even a few minor supporting roles. McAvoy shifts his speech, posture and facial expressions with ease, but — even more impressive — always shows us the crack in each facade.

The film’s other major asset is Taylor-Joy (“The Witch”). She’s a haunting presence as Casey, a black-haired, black-eyed misfit whose own troubled past, seen in flashbacks, gives her a unique empathy for her captor. Although “Split” repeatedly asks us to believe that the girls are too scared to fight back, grab weapons or flee through open doors, Taylor-Joy is so intriguing that we kind of want her to stick around.

Shyamalan takes an inventive approach to the controversial theory of Dissociative Identity Disorder. Betty Buckley plays a renegade psychologist, Dr. Karen Fletcher, who believes each “alter” is a truly different person, even physically. When Dennis/Hedwig/Patricia talk of The Beast — perhaps a 24th personality? — you might feel a little shiver down your spine.

As for the film’s ruinous final moment, involving a pointless reference to another Shyamalan movie and a celebrity cameo, it’s a real shame. Just when you were enjoying this clever, creative filmmaker, the dunderhead within takes over.