★★★
(M), 117 minutes
M. Night Shyamalan's rehabilitation from blockbuster failure, which began with 2015's found-footage thriller The Visit, continues with Split, an untidy but often effective horror film. Reflecting Shyamalan's reinvention of himself as a low-budget filmmaker, it's a film about identity and using fear to become who we truly need to be, not to mention quite possibly the worst doctor and patient relationship ever.
Kidnapped without word or explanation after a birthday party, three teenage girls from Philadelphia – Casey (Anya Taylor-Joy), Claire (Haley Lu Richardson), and Marcia (Jessica Sula) – find themselves in the company of a man who, in turn, has the mannerisms of a menacing thug, an English dame and a nine-year-old boy. This is Kevin (James McAvoy), who suffers from dissociative identity disorder (DID). He has 23 personalities, with a 24th, called "the Beast", on its way.
Shyamalan, whose breakthrough feature was 1999's The Sixth Sense, is working on a concise budget again, but here he tries to tell too many stories. There is an excess of scenes with Kevin, a vessel for differing personalities who have an elaborate hierarchy, visiting his therapist, Dr Fletcher (Betty Buckley). In her eagerness to convince the world that DID is so real that a body will have differing characteristics for each personality, she has failed to notice that Kevin has really gone off the rails.
The real terror and intrigue – as opposed to clue planting for the inevitable Shyamalan twist(s) – lie with the young women locked away in an underground lair. Claire and Marcia want to fight back, but Casey refuses, calmly detailing his advantages. She's compliant, but also observant and well-versed, and childhood flashbacks add another layer of storytelling to a narrative that sometimes feels as if it's marking time until the final act ramps up.
Taylor-Joy has a sense of self-possession so fierce it's frightening, and, after headlining the remarkable 2015 period horror film The Witch, her performance here does a great deal to pull Split above its sometimes queasy use of unspeakable trauma as a plot point. McAvoy gets the showy turn, transforming himself with each sighting of Kevin, but Taylor-Joy brings a horrifying stillness to the movie.
One of Kevin's personalities is a cleanliness freak who confiscates the captive's dirty clothes – half-naked females is one horror trope the film didn't need – but Shyamalan's technique is sharper than his writing. He teases with vertical and horizontal slits of available sight, while his camera ominously encroaches. Thankfully, the director still has the ability to gently personalise his lurid revelations: a brief shot of Kevin's bathroom reveals dozens of toothbrushes, each awaiting its owner.