Creatively speaking, if not financially, the Divergent series is less a franchise than a quagmire, an unwinnable war that nonetheless must be fought until the bitter end. And like all quagmires, the terrain has been hostile from the start: Based on Veronica Roth's bestselling novels, the films have tried to advance a "Chosen One" narrative through the awkward rigging of a dystopian "faction" system that, at best, only makes sense when vast swaths of the screenplay are carved out to explain it. Three-quarters of Insurgent, the most recent entry, were devoted to opening a mystery box from "The Founders"; the last quarter asked the audience to sort through the tortured logic of its contents.

Based on the first half of the last book in the trilogy — which has been cleaved in the lucrative style of YA finales like Harry Potter, Twilight, and The Hunger Games — Allegiant is substantially more exciting than Insurgent, if only for clearing up the confusion a bit. And all it takes to explain it is an audio recap in the opening title sequence, two or three holographic video presentations, a 10-minute Jeff Daniels monologue, and a meeting with a special elite counsel. That's relatively efficient work for this series, but it brings the world of Divergent no closer to allegorical significance, other than a blanket condemnation of baffling totalitarian governments.

When we left off, an uprising hastened the collapse of the faction system in Chicago, with "factionless" leader Evelyn (Naomi Watts) capping Janine (Kate Winslet), the dictator hell-bent on supporting it. In a classic "meet the new boss" scenario, Evelyn starts ordering public executions of Janine's loyalists and shuts down access to the wall, despite the mystery box offering the promise of a civilization on the other side. But that doesn't stop Divergent hero Tris Prior (Shailene Woodley) and her friends—love interest Four (Theo James), weak brother Caleb (Ansel Elgort), Dauntless comrade Christina (Zoe Kravitz), and the duplicitous Peter (Miles Teller)—from following their curiosity and busting out anyway.

What they find is somehow bleaker than the ruins of Chicago, an arid red hellscape that looks like Mad Max: Fury Road restaged on the surface of Mars. But soon enough, they're picked up by high-tech soldiers and whisked to a pocket of humanity that resides in that most dystopian environment of all — Chicago O'Hare International Airport. Once there, Tris' status as the only "100% pure" specimen from Chicago makes her the key figure in an initiative to restore humanity after a genetic experiment gone awry. She'll just have to trust the director of this initiative, David (Daniels), the latest in a long line of shifty authoritarian figures in the Divergent series.

The mythology gets more complicated still, on all fronts, from the ins-and-outs of genetic engineering to the civil war that breaks out in Chicago between Evelyn's government and former Amity leader Johanna (Octavia Spencer). In typical Divergent fashion, all of this intrigue requires long-winded explanation, which inevitably stalls the action. But compared to the endless wheel-spinning in Insurgent, Allegiant keeps the action set pieces coming at a regular clip and ventures into unknown territories, where the effects render worlds that are both sleekly futuristic and ravaged by the sins of the past.

Of the cast, only Teller appears to be having any fun, jesting his way through world-changing crises like a Jeff Goldblum character. The rest of Allegiant, like its predecessors, is handled with deadly seriousness, which has never served a science-fiction universe that doesn't hold up under scrutiny. Allegiant may tidy up the ornate logic of the Divergent series, but a clearer understanding of the faction system and its roots is not necessarily a more compelling one. Unlike the Panem of The Hunger Games saga, which takes real historical tyrannies as an inspiration, there's no getting around the fact that Divergent is a clunky apparatus built around a trendy "Chosen One" type. It's now possible, after Allegiant, not to be confused anymore about how that apparatus works. To be entertained by it is another matter.

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