Split review: James McAvoy throws himself into multiple parts in M Night Shyamalan's taut, grisly comeback

You’ll spend it largely in the company of James McAvoy, who plays Kevin – and also Barry, Dennis, Miss Patricia, nine-year-old Hedwig, and some others too. These characters are among the 23 inhabitants of the overcrowded mind of Kevin, an odd-job man who suffers from dissociative identity disorder.

Known until recently as multiple personality disorder, it’s the very cinematic psychiatric ailment which gave us Mrs Bates in Alfred Hitchcock’s Psycho and Bobbi in Brian De Palma’s Dressed to Kill  – and McAvoy, who looks just darling in a twinset and locket, does enough peeped-upon cross-dressing here to leave you in no doubt of what Shyamalan’s aiming at. (Though for what it’s worth, it feels more like a dry reference to the classics than bona fide kink.)

Two of Kevin’s less appealing personae, obsessive-compulsive Dennis and passive-aggressive Miss Patricia, have staged a psychological coup in order to prepare the way for ‘The Beast’, a brand new and mostly shirtless 24th identity – think Mr. Hyde meets Magic Mike – with a fetishistic hunger for innocent flesh. As such, the film begins with Dennis-Kevin kidnapping three teenage girls and imprisoning them in a hidden lair until sacrifice o’clock.

One of the trio is Casey, superbly played by Anya Taylor-Joy – who’s clearly now the go-to young actress for willowy vulnerability with a shimmer of slyness, following her outstanding recent work in Robert Eggers's horror masterpiece The Witch.

Through big eyes that shine from behind a tangle of black hair, loner Casey is the only captive who seems to connect with Dennis in any of his guises: the more popular and (intentionally) shallower Claire and Marcia, played by Haley Lu Richardson and Jessica Sula, are there largely as a semi-dressed chorus, to panic, cower, flash skin and scramble for escape as needed.

Kevin’s hideout is more or less the dank chamber of horrors you expect – though Shyamalan, teamed with cinematographer Mike Gioulakis (It Follows), find some haunting angles on it: not least a fluid track-back down a seemingly endless corridor which slows a previously frantic escape attempt to the dark and treacly tempo of a nightmare.

The swells of claustrophobia are also regularly punctured by flashbacks to Casey’s own childhood and Kevin’s daily visits to his doctor (Betty Buckley), whose job it is to reassure us – even as she pants over Skype that the condition allows Kevin et al to “change their very body chemistry with their thoughts!” – that there might be an academically credible excuse for all this. 

Is there? Well, no – and no-one seems to have suggested otherwise to McAvoy, who throws himself into his part 24 times over, in a performance that develops the flair for grotesquerie he last memorably flexed as the bipolar Edinburgh cop in Jon S Baird’s Filth. He’s all flicky eyes and pursed, maiden-aunt lips one moment, and pre-pubescent coyness the next – and with a less naturally engaging star, it’s easy to picture the film’s stagier gambits falling flat.

As perhaps they might have done on a flabbier budget. Split is a taut and gristly creation, and was co-produced by Jason Blum, whose company Blumhouse was also responsible for Joel Edgerton’s The Gift: another controlled psychological thriller built thriftily, but also to last.

After the asinine bloat of The Last Airbender and After Earth, and the abortive down-and-dirty comeback of 2015’s found-footage horror The Visit, this measured, diligently crafted register feels like Shyamalan back on home turf.

Seemingly chastened by the intervening years, even his cameo’s self-deprecating, as a dopey security camera operator whom another character points out is getting flabby in his middle-age. Thank goodness his technique is crunching its way back to a six-pack.