I've been onboard with the dystopian adventures of Tris Prior (Shailene Woodley) in her post-apocalyptic future Chicago, but this third outing is a disappointing downfall from the first two films. Here, in Allegiant, the reasons for the apparently precarious foundations of her existence are revealed, the metaphor suddenly fails as a metaphor and the concrete reality it is replaced by is far less intriguing. Classified as dangerously "Divergent" in a society where almost everyone is easily slotted into five "Factions," Tris had – in the first two films, Divergent and Insurgent – been leading a fight in Chicago to regain control from a ruthless leader who was cracking down on Divergents and the rogue Factionless. That culminated with the revelation that Chicago was, in fact, the site of a grand experiment, that the rise of Divergents meant the experiment had been a success, and that the people of Chicago were welcome to rejoin the rest of humanity outside the wall that has contained them.
This is the big decision to be made as Allegiant opens: Shall they go out to meet the people who have been experimenting on them, and, if so, how can such people ever be trusted? However, Factionless leader Evelyn (Naomi Watts), who is effectively in control of the city and inciting mob hatred against the defeated Erudite Faction, has pushed Chicago to the brink of total civil war. So off go Tris, her boyfriend and lieutenant Four (Theo James) and a handful of others, over the wall and through a blasted and inhospitable hell-scape to see what, and who, is out there.
The small pleasures of receiving answers to the mysteries of Tris' world are instantly overwhelmed by the practical considerations of what those answers bring ... and those aren't, alas, further questions and more intriguing mysteries, just accidental conundrums of plot and character that smarter scripting and a more cohesively considered science-fiction culture-scape could have avoided.
There is one huge plot hole here that brings the entire story crumbling down into its obviousness, one that will echo through the whole rest of the film: Why didn't those experimenters just do X?
Between that plot hole and the loss of the metaphor about conformity that has informed Tris' journey up to now, all we're left with – if we want to find anything of substance and meaning in Allegiant – is a weak and barely acknowledged philosophical clash between Tris' young and eager idealism and the messy, complicated reality she discovers beyond the wall. But even that quickly gives way to the dullest sort of black-and-white, good-versus-evil battle that throws away the potentially complex concepts it had been playing with and reverts to a simplistic box-checking exercise in action filmmaking. The ending is so foregone as to be anticlimactic ... and there's still another movie to wade through.