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It’s actually kind of remarkable how much genuinely good cinema the glut of young adult fiction adaptations has produced. Harry Potter is obviously the standout here. Off at the opposite end, the Twilight saga was the one real disaster. Of the three movie series dealing with future dystopias, The Hunger Games showed depth and complexity, and the two Maze Runner movies have proven to be surprisingly solid entertainment.

Which brings us to the Divergent series – and its third installment, Allegiant. The franchise wears its heart on its sleeve. Its setting, in which a post-apocalyptic human society has organized itself into five castes based on individuals’ aptitudes (intelligence, courage, selflessness, honesty and so on), is a pretty obvious metaphor for the cliquishness and tribalism of high school and college, as well as the expectations parents and society can have for children. But the movies have avoided getting too bogged down in all that, and have consistently found new angles on the premise and odd new corners of this fictional society. It’s not as strong as Hunger Games, but it’s respectable.

Allegiant continues that trend, but unfortunately – and despite the biggest whizz-bang production values yet – it’s also a step back from its predecessors.

The movie picks up where Insurgent left off. The caste system has been overthrown, and the population of Chicago has just discovered they aren’t the only remaining members of the human race. Out beyond the wall that surrounds the city are other people, who actually designed the enclosed city and its caste system as a kind of grand experiment. The “divergent” – people who don’t fit into any of the five groups – have been treated as flaws in the system. But now it turns out they were the point of the experiment the whole time.

Tris (Shailene Woodley) is a divergent who’s spent the last two films battling the cast system alongside her comrade and lover Four (Theo James). She’s determined to get beyond the wall to see what’s out there. But no sooner is victory achieved than Evelyn (Naomi Watts), the leader of the rebels and Four’s mother, puts the city on lockdown. As the rebellion disintegrates into executions and mob rule, and Johanna (Octavia Spencer) leads a protest movement, Tris and Four escape over the wall and journey out into a blasted post-nuclear wasteland. Along for the ride is Tris’ brother Caleb (Ansel Elgort), who betrayed her in the previous film and is now on thin ice; their scheming sometime-ally sometime-enemy Peter (Miles Teller); and Tris’ good friend Christina (Zoe Kravitz).

Chicago has always been an odd yet captivating vision in these films: a bombed-out cityscape partially retaken by nature, with advanced technology and architecture scattered throughout. But what Tris and her companions find out in the wasteland is a genuinely futuristic society, lead by the mysterious David (Jeff Daniels), which has set out to repair the human race’s genetic material. Eventually Tris must decide whether her loyalties lie with David and her newfound home, or with the people of Chicago and their incipient civil war.

There are some good ideas floating around, particularly the question of whether our looming future of personal genetic modification might come with a few downsides we’d eventually have to recover from. This backstory also gives the series a new caste system – now between the genetically “pure” and the “damaged” – to replace the old one, and allows Tris to bring her previous experience with social division to bear on this new situation. (There’s one or two grand speeches in this regard, but thankfully they’re kept to a minimum.) Enough darkness is thrown in to lend the proceedings weight without descending into pretentiousness.

The strongest part of the Divergent series has always been the relationship between Tris and Four, and Allegiant tests it in a new way by shipping the two off to different camps in this new society and giving them very different perspectives. The possible rift between them lends the story real emotional stakes.

Director Robert Schwentke and his fellow filmmakers take full advantage of their new setting, inventing a wealth of advanced ships, gizmos, weapons and cityscapes. Allegiant looks big and vibrant, and the score by Joseph Trapanese has the same sort of pulsating sci-fi etherealness that M83 brought to Oblivion.

The big downside is that the script feels like all wind-up and little payoff, at least character-wise. (There’s certainly plenty of action.) Divergent and Insurgent were both coherent and self-contained narrative arcs, but Allegiant feels more half finished. And that’s probably because it is: Taking their cues from previous series like Harry Potter and The Hunger Games, the filmmakers broke the book Allegiant – the final installment in Veronica Roth’s trilogy – into two parts, of which this film is the first.

Those other franchises handled this gambit well enough, but Allegiant suffers for it. Of the three films, it’s the only one that’s an obvious place-holder or in-between episode. In many ways, it’s the tightest and most well-produced installment in the series; but when Allegiant ends, it feels more like it’s being told to wrap things up.