A man with multiple personalities abducts three teenage girls and subjects them to a gruesome fate – they are going to be acted at beyond endurance

In the comic thriller, Split, a man with multiple personalities (James McAvoy) abducts three teenage girls and locks them away in a windowless, subterranean cell. Classy, eh? A premise that is both straightforwardly exploitative and trivialises mental illness.

Once in the cell the girls are going to be subjected to a gruesome fate – they are going to be acted at beyond endurance. This is like a Saw movie where Jigsaw is revealed to be the undiscovered, non humourous Jim Carrey performing his showreel.

James McAvoy is the last actor you’d describe as a ham. Indeed, I’d say he was one of the best screen performers around, but the role calls on him to play a selection of the 23 trapped personalities, jumping from sinister to camp to child to female. He tries to play it as real as possible but it is written as a ham sandwich and he can’t help himself.

The role is effectively Mrs Doyle egging him on to chew some scenery: go on, go on, go on, you will, you will, you will, sure, it’s just a little scenery.

Split is both more interesting and much duller than you’d expect – it takes the high road and the low road, but neither of them effectively. It does appear to have some a genuine interest in the disputed field of Dissociative Identity Disorder (DID), as something more than a convenient source of menace.

It isn’t predictable either: granted, there is one character whose function in the plot you will guess the moment she appears on screen but otherwise the film does a fine job of subverting expectations.

But it isn’t remotely scary. The first and most obvious expectation is that it will be an exercise in claustrophobic suspense. But no, the film is too antsy to ever stay in that cell with the girls for more than a few minutes at a time. The first chance it gets it is off around town, or flashing back into a captive’s past, so that’s most of the tension evaporated.

It is also too long and slackly plotted. The title may come to reflect audience reactions to it – I can foresee it provoking both rabid hate and enthusiasm.

Rating: 2/5 stars