Dubious story, sloppy writing, great (McAvoy) acting

Rating: 6/10 (26 January 2019)

I'll start by qualifying my rating...
The basic movie, I feel, deserves probably a 5 out of 10, but McAvoy's impressive acting has convinced me to elevate that to a 6.
The original 5/10 I'd considered is primarily due to how it spontaneously decelerated into a rapid slow down in its latter half. As a rule, a good indication/symptom of such a surprising turning point is when the viewer starts getting fidgety. Well, I got fidgety.
Although the storyline did contain some minor flaws in rationale in its first half, the major turning point, for me, came when Dr Fletcher - on visiting the nutter (Kevin) - realised something was seriously wrong and decided to investigate for herself. This was the film starting to get ridiculous.
Now any intelligent person, especially a woman (naturally/generally less robust, and therefore more vulnerable, than a man), and an elderly one at that, would keep calm, leave the place as was obviously able to easily do... and call the police, citing her qualification as a psychologist. But no, the character had to go and investigate for herself, thus risking her own safety and the consequent safety of any others she suspected of being incarcerated there. So, what happens? Yes, she gets killed... and this type of scenario has become a film cliché now.
Another ridiculous scene was the girl undoing a bolt on the outside of her door by using a length of weak coat-hanger wire... weak mainly because it was unfolded into a single strand!
The film left many key points unanswered. What happened to Claire's father? Where were the girls' families in all this? There was a (possible) 'suggestion' that Casey turned her uncle (who, it's depicted, imposed a litany of ongoing sexual abuse on her from a very young age) in at the end of the movie, having now found her epiphany and awoken from her personal guilt, self doubt and denial... but it wasn't made clear.
One of the major flaws was that there was no clarity as to what this film was. Was it supernatural? Was 'The Beast' reference to the Devil? The indication, at the end, was that Kevin took on the 'personae' of the predator zoo animals. Okay, so if it wasn't supernatural, how could Kevin have performed the superhuman/superhero acts that he did, like jumping barefoot off the roof of a train, running faster than a Cheetah, scurrying along a tunnel ceiling and easily clambering up vertical walls like SpiderMan or a fly or... something supernatural...?
Carey's epiphany was - I suppose - nicely highlighted towards the end when she was rescued/found in the cage. As she was helped out, the sun shone in from the window above and lit up the scene. This seemed to comply with both her epiphany and the "light" that Kevin discussed numerous times with his shrink... Dr Fletcher.
As for eating the girls... well, unless (as a non-supernatural "Beast") he had jaws and the appropriate animal teeth, this would've been virtually impossible, and yet he seemed to have eaten Marcia (without chopping her up) and at least some of Claire while still alive. Did she survive? Something else the writing didn't clarify, although we can probably assume she had been sufficiently devoured.
My scoring for this movie was elevated from a probable 5-6/10 to 7/10 thanks to McAvoy's excellent performance in the portrayal of a multitude of different personalities.
Although I'm not particularly keen on McAvoy, I do respect him as a very fine actor, and I think he did brilliantly in this. However, although his brilliance elevated the movie somewhat, it couldn't fully excuse the sloppiness of the story and the dubious writing (particularly later in the film).
The closest I've seen to McAvoy's superb psychological performance is a similar (but less personalities) portrayal of multiple personality disorder by Jonathan Banks in an episode or two of Hill St Blues in the 1980s. Although Banks did a helluva great job, I'm not sure he received the accolade he - in my opinion - deserved.
Anyway, the film did captivate my interest for the first half, but like so many films these days, it became both boring and somewhat ridiculous in its latter half.
I could be wrong, but was there a similarity to "The Silence of the Lambs" at the end of the movie, with Bruce Willis seated on a bar-stool, suggesting that the story is not yet ended and that the true monster of the story is Willis as "Dr Glass"... just as Lecter was the true monster in SotL (particularly poignantly so at the end)...?
The film - I'd say - is worth seeing... if for nothing else, then at least for McAvoy's performance.