M. Night Shyamalan has had a bit of a bad run lately. After the big-budget debacles “After Earth” and “The Last Airbender,” you’d have been forgiven for never committing to another Shyamalan film again.

But I am delighted to report that “Split” is the movie that may change your mind.

“Split” begins with the sudden abduction of Casey (Anya Taylor-Joy, fresh off a memorable performance in last year’s “The Witch”) and her two teenage friends from a mall parking lot. They find themselves trapped in an industrial basement somewhere deep underground, held hostage by Kevin (a superb James McAvoy).

It turns out that Kevin suffers from dissociative identity disorder, manifesting twenty-three separate personalities—gregarious Barry, professorial Orwell, obsessive-compulsive pedophile Dennis, maternal Patricia, childish Hedwig, and over a dozen others. What’s more, these personalities are aware of each other’s existence (conceiving of themselves as seated in a circle of chairs, from which they can each emerge into “the spotlight” and briefly take control of Kevin). And if that weren’t wild enough, some personalities can actually mimic each others’ mannerisms, making it hard to tell who’s really in control.

It’s an outrageous, over-the-top story, but somehow Shyamalan manages to pull it off with flair. “Split” is gripping in a way none of his films have been since “Signs,” building to a crescendo of gut-wrenching horror that pulls very few punches. This hardly feels like the same director who gave us the pedestrian “Lady in the Water”: old-school Shyamalan is back in action, and it’s fantastic.

Totally-bonkers premise notwithstanding, strong acting is the real foundation of “Split.” Opposite McAvoy (whose personality-shifting performance is the stuff of nightmares and Oscars alike), Taylor-Joy proves herself a surprisingly capable “Final Girl.” Casey is as broken in her own way as Kevin, and their interactions—chilling strategy juxtaposed against total insanity—are mesmerizing in a Hannibal-and-Clarice sort of way. Reasonable minds may disagree on whether or not Kevin’s psychotherapist, Karen (Betty Buckley) adds much to the narrative: she provides most of the film’s exposition, which initially heightens the drama, but most of her revelations could’ve been inferred from watching Kevin in action. At times, “Split” feels a touch too quick to hold the audience’s hand…but this is a minor quibble.

There are also some interesting thematic dynamics going on under the surface here: Kevin’s story is perhaps best described as a secular version of “The Exorcist,” in which more-or-less malevolent personalities jockey for control of a victim’s conscious identity. Shyamalan doesn’t have much time for theories of mind—which is all well and good, “Split” is complicated enough—but it’s a nice flourish that evokes some of the best of old-school horror. (Fair warning: “Split” is one of the grisliest PG-13 films I’ve ever seen. The R-rated “The Conjuring” was quite a lot tamer.)

I’ll refrain from spoiling too much, but suffice it to say that “Split” is entirely worth seeing if you’re a fan of Shyamalan’s early-period work, or of psychological horror-thrillers in general. Hitchcock would be proud.

Welcome back, M. Night. We’ve missed you.

VERDICT: 9/10
One of the most compulsively watchable thrillers I’ve seen in the last year. Highly recommended.

Normalized Score: 7.9