Split

After a few badly received sci-fi blockbusters, M. Night Shyamalan returned to his earthier style of filmmaking with 2015's The Visit and now this edgy psychological horror romp. It's a genuinely freaky movie, packed with unsettling touches and wonderfully intense performances. And yet there's a nagging sense that the filmmaker is using a very real mental health issue for cheap thrills. Dissociative identity disorder, also known as split personality, is genuinely devastating, but here it's played for blackly comical chills.

The man suffering from this condition is Kevin (James McAvoy), and he has 23 identities battling for supremacy inside him. The ringleader is Dennis, a psychopath who is working in league with fellow alter-ego Patricia to kidnap three young women, the abused outcast Casey (Anya Taylor-Joy) and two classmates (Haley Lu Richardson and Jessica Sula). As these teens try to use his personalities against each other to escape, Kevin is also attending sessions with his psychiatrist Dr Fletcher (Betty Buckley), an expert on his condition. And she has no idea what he's actually up to. Or that all of his personalities are terrified of a menacing identity they call the Beast.

Shyamalan is an expert at dropping clues into each scene, packing the dialog with innuendo and encouraging the actors into giving performances that suggest at unexpected connections and histories. As the film progresses, both Kevin and Casey reveal the most telling details of their grim pasts, allowing Shyamalan to gleefully crank up the tension. And the result is enjoyably creepy, keeping the audience off-balance with a plot that's impossible to predict and plenty of shocking mayhem along the way. At the centre, the audience is able to identify with Taylor-Joy's thoughtful Casey, a girl who has survived a nasty childhood and is determined to get out of this situation before it turns even more horrific.

Of course, the film's centrepiece is McAvoy's wonderful collection of performances as Kevin's various personalities. Energetic, funny, charming and terrifying, McAvoy goes for broke to bring each one to vivid life, adding hilariously camp touches and childlike innocence, as well as genuine malevolence. So it's a shame that the character tips over into silly movie villain mode in the final sequence, rather than going for something a bit darker and deeper. But it's an enjoyable freak-out while it lasts, and in fine Shyamalan style he holds back a little gift for his fans until the very end.

Watch the trailer for Split: