The third installment of M. Night Shyamalan's Eastrail 177 trilogy (preceded by Unbreakable and Split) is, on paper, a brilliantly meta-exploration of superhero convention. Glass sees psychiatrist Dr. Ellie Staple (Sarah Paulson) institutionalise the trilogy's three leads, believing they all suffer a similar delusion that makes them believe they have superhuman abilities, and trying to convince them to embrace reality.

But conveniently, by bringing together the physically indestructible Overseer (Bruce Willis), intellectually brilliant but physically fragile genius Elijah P. Glass (Samuel L. Jackson), and 24-personality containing Kevin Wendall Crumb (James McAvoy) - who can transform into the wall-scaling, flesh-eating, animalistic Beast - Dr. Staple gives us our archetypes: the hero, the mastermind, the villain. And Elijah, a comic book expert, is eager to use their proximity to engineer the showdown he believes they are all destined for. Questions of faith and self-belief and the promise of an epic superhero battle? Exciting!

Or it would be if Shyamalan wasn't destined to over-explain every minute point like a Leaving Cert student who has been trained to explicitly refer back to their thesis statement in each paragraph. The exposition isn't just patronising to an audience who have become au fait with comic book convention over the past two decades; it also slows the action to a sluggish crawl. It's like that comedy maxim: over-explaining a joke - or here, pop culture archetypes - is like dissecting a frog. You don't really learn anything, and the frog dies.

This is a real shame, as there are brilliant flourishes. Through distinctive colour palettes and comic book framing, Shyamalan evokes certain themes and the asylumıs claustrophobia. Willis phones in his performance, but Jackson exudes an enjoyably hammy energy, while McAvoy's hold over his character's 'horde' of stereotypical personalities remains entertaining.

But eventually, Shyamalan will have to confront his delusion that he's so much smarter than his audience. It's been a while since he convinced anyone.