Spoilers follow ...

Rating: 2/10 (2 February 2017)

Two smartphone distracted girls and their 'weird' friend are kidnapped by an unknown assailant who carries out the action without any emotion whatsoever.
'Barry' is a model employee. He's been ill, but is better now. Doctor Fletcher (Betty Buckley) says this. We learn of 'Barry's' disorder because Fletcher is trying to widen awareness for his condition. The information about what is known as 'DID' is staggered throughout, at length, and her scenes are interspersed with 'Barry' and his other personalities presenting themselves to his three prisoners. One of these is an upper-class woman called 'Patricia', another is an irritant called 'Hedwig', another is a nuisance called 'Dennis' (who likes to watch girls dance naked). In reality, his name is Kevin Wendell Crumb (James McAvoy), and he has 23 personalities.
Despite claims that, for example, if one personality is a weight-lifter he possesses the strength of a weight-lifter whilst other shared personalities do not, McAvey doesn't have the physical presence to portray anyone that couldn't just be over-powered by the three girls – or even just one of them (with a more sustained battering than just hitting him once and then turning their back on him, something that happens more than once). Despite the theatrical rolling eyes, the lisp, the change of clothes, he simply isn't frightening. His endless talking about himself makes it clear that his characters are a lot more interesting to him than to the audience – or at least, this member of it. I can appreciate a committed performance, but sadly he leaves me cold.
Perhaps to balance out Kevin's multiple characteristics, the three girls have only one personality between them. Being the allegedly 'weird' one of the trio, it is Casey (Anya Taylor-Joy, who had been so good in 2015's 'The Witch') to whom 'Dennis' is attracted, because of course weirdness is an elite exclusive club that joins every outsider together, provided you're pretty enough ('the broken are the more evolved,' apparently). Luckily for flesh fans, one of Kevin's personalities suffers from OCD, necessitating the young captives to remove much of their 'dirty' clothing. Another box ticked.
There have been accusations that 'Split' is offensive to sufferers of mental health disorders. In an age where being offended is a competitive sport, presumably any piece of fiction involving death, for instance, is offensive to anyone who has ever suffered bereavement and therefore 'shouldn't be allowed'. This is a point of view that stifles creativity, fiction, drama and/or many levels of art. That is not the problem with 'Split' in my view. It is an idea that is ripe with potential but simply stretched out very thinly over almost two hours with very little incident. In fact, the kidnapping of three girls is the only incident. Endless scenes of talking about 'Barry's' condition isn't entertaining, frightening or effecting. It very quickly becomes dull and stays that way.
Director M. Night Shyamalan had a great success with 'The Sixth Sense' in 1999, especially its twist ending. Subsequently, all his films have ended with a similar surprise, each one less effective than the last. If you make it to the end of this, there is a revelation that (SPOILERS) Kevin's affliction appears to be supernatural. 'The Beast' is physically bulkier than his other personalities, can hop from wall to wall and is impervious to bullets. This ends with a reference to Shyamalan's 'Unbreakable' via a Bruce Willis cameo which pre-supposes you are on familiar terms with that film, which is presumptuous, as this is not billed as a sequel.