M. Night Shyamalan — a name that triggers filmgoers and invites relentless parody. Since “Unbreakable,” his batting average has been much less than stellar, with “The Happening” and “The Last Airbender” lowering the bar for Shyamalan and for movies in general.  

Unlike many of his previous films, Shyamalan’s “Split” has two important twists. Avoid spoiling the first for yourself, because the second twist is that “Split” is actually good. This taut and thrilling B-movie is a return to form for Shyamalan. It features an engaging narrative that avoids his worst tendencies and taps into his ingenuity and creativity.

The film benefits most from its setting: a creepy basement where Kevin (James McAvoy) has imprisoned three girls — Casey (Anya Taylor-Joy), Claire (Haley Lu Richardson) and Marcia (Jessica Sula). The cramped setting forces Shyamalan to be creative, and half the fun of “Split” comes from watching the characters work to outsmart their captor and escape.

The other half comes from McAvoy’s performance, because Kevin has dissociative identity disorder. He houses 23 personalities, ranging from an amicable fashion designer to a diabetic woman. Three of his personalities — the germaphobic Dennis, the religious Patricia and the nine-year-old Hedwig — have assumed control over the others, and they plan to feed the girls to Kevin’s emerging 24th personality: the Beast.

The role of Kevin is an acting Olympics, and McAvoy wins the gold in every event. He deftly moves from personality to personality with startling proficiency, capable of making us laugh in one moment and then emanating malevolence in the next. Thanks to his superb use of his body and voice, McAvoy balances the character’s more outlandish and hammy aspects with fine-tuned vulnerability. It’s clear Kevin doesn’t want to go down this dark path, but his villainous side grows stronger in spite of his efforts to control it.

Recognizing the conflict within Kevin, Casey attempts to turn his personalities against each other. What ensues is a cat-and-mouse game where both characters find themselves at wits’ end, and they discover they have a lot more in common than they initially realize. Like Kevin, Casey is an outsider, and Taylor-Joy subtly conveys the same pain in her distant gaze as McAvoy’s. Casey’s flashbacks to a childhood hunting trip inform her actions against Kevin, and as their face-off reaches its climax, “Split” hits some unexpectedly emotional notes. 

The film benefits from excellent camerawork from Mike Gioulakis, the director of photography of “It Follows.” He carries over that film’s crisp look and drawn-out shots to “Split” with great effect, lingering on the more horrifying moments and letting them play out. The music by West Dylan Thordson is similarly spare, allowing the actors and writing to evoke the dread Shyamalan aims for.

“Split” succeeds on its unwillingness to take itself seriously. The occasionally clunky dialogue, ridiculous portrayal of mental illness and long moments of exposition may be distracting, but they are also largely forgivable because the film just wants to have fun. Shyamalan takes “Split” to ridiculous heights that seem to require a leap of faith on the part of audiences. Join him, and your questions will be answered by the end in one fell swoop.