Tough as nails, achingly fallible, and wholly unsparing, "Prisoners" doesn't let go from its vise grip even after its chillingly provocative final shot. To assume the film is a revenge exploitationer, as it kind of looks like from its advertising, is to not give it nearly enough credit. What director Denis Villeneuve (2011's "Incendies") and screenwriter Aaron Guzikowski (2012's "Contraband") have created is challenging and multilayered—a complex morality play, a riveting thriller, and a tastily labyrinthine mystery all in one. It might run nearly two and a half hours, but it earns every one of those captivating minutes.

In a middle-class Pennsylvania suburb, the Dover family—Keller (Hugh Jackman), wife Grace (Maria Bello), 16-year-old son Ralph (Dylan Minnette), and 8-year-old daughter Anna (Erin Gerasimovich)—have come to spend Thanksgiving with their friends down the street, Franklin Birch (Terrence Howard), wife Nancy (Viola Davis), teenage Eliza (Zoe Soul), and little Joy (Kyla Drew Simmons). One moment, Anna and Joy are precociously singing a fractured Christmas carol ("Jingle bells, Batman smells...") in front of their parents, and the next they are gone. Keller believes they might have gone to his house to search for a whistle Anna had lost, but they are nowhere to be found. Ralph mentions a strange RV he had stopped the girls from climbing on earlier, but it is now gone. It doesn't take long to locate the vehicle, but when Detective Loki (Jake Gyllenhaal) arrests the driver, the mentally handicapped Alex Jones (Paul Dano), he soon realizes he doesn't have any concrete evidence to keep him locked up. A distraught Keller, having reason to believe Alex knows where the kids are, abducts him at gunpoint and locks him up in his now-abandoned former residence. When Franklin and, later, Nancy learn that Keller intends to torture the young man as a means of forcing him to talk, they know it to be wrong, yet see it as the only way to possibly get their daughters back.

At initial glance, "Prisoners" would appear to travel upon familiar turf, complete with snatched children, grieving parents, an investigation that leads to a handful of suspects, and the extreme decision to seek a sort of eye-for-an-eye vigilante justice. All of that is present and accounted for, and yet director Denis Villeneuve is mindful of viewing his characters through a prism of colors that move far beyond black and white. In this onscreen world, much like our own, there are no easy answers. Keller oversteps an ethical boundary the moment he opts to take matters into his own hands, and then crosses the point of no return when he has beaten Alex's face to a swollen pulp. These actions are not necessarily Franklin and Nancy's own, but they are guilty of their own desperate choice to not let him go if it means saving the lives of their loved ones. If these dubious matters are worth debating, they only skim the surface of an organically twisty narrative that goes in directions impossible to anticipate. Like a literary page-turner, one cannot wait to see how things progress and evolve. Meanwhile, a police procedural is in full force as Detective Loki is drawn into a web of buried secrets and sordid criminal behavior within the town that seems to point the finger at someone else altogether, an intensely strange reptile owner named Bob Taylor (David Dastmalchian).

Without much in the way of factual character development, Jake Gyllenhaal (2012's "End of Watch") presents what mostly feels like a full life in the space between when his Detective Loki clocks in and out of work. Having always been able to solve the cases he's been assigned, his latest investigation edges toward obsession. All of the pieces of the puzzle seem to be in front of him, but he can't quite make them fit. Gyllenhaal is terrific in the part, tiny details like Loki's tendency to blink his eyes in heightened situations natural extensions of a role that might have otherwise been deemed undernourished. As Keller, Hugh Jackman (2012's "Les Miserables") is obviously much better tested and emotionally available in morally prickly dramas such as this than in his weary umpteenth turn as Wolverine. He is supported by an ensemble cast that could not conceivably be any better. Despite not having nearly as much screen time, Viola Davis (2012's "Won't Back Down"), Maria Bello (2010's "Beautiful Boy"), Terrence Howard (2013's "Lee Daniels' The Butler") and Dylan Minnette (2010's "Let Me In") provide keenly stirring snapshots of their own personal coping processes in a time of tragic uncertainty. Not to be outdone, Paul Dano (2012's "Ruby Sparks") and Melissa Leo (2013's "Olympus Has Fallen") are veritable chameleons as, respectively, endangered suspect Alex Jones and his supportive Aunt Holly. Both actors play their parts with a subtle command; disappearing into the shoes of people entirely unlike them, they are aware that going big isn't necessary when they have the ability to walk so vividly in them.

"Prisoners" is evocatively lensed by cinematographer Roger A. Deakins (2012's "Skyfall"), the encroaching bitterness and nasty late-autumn weather setting on lives already stranded in internal frigid despair. There is a special texture to its season-specific atmosphere and the small-town milieu on display that most films tend to forget about—the difference between a genuine artist and a less-talented work-for-hire. There is so much going on within the taut framework of "Prisoners" that it's really quite special to watch everything unfold as it does. Though the finale at first appears to be too easily letting a pair of characters off the hook, it is in hindsight that one realizes this is a part of director Villeneuve's style. He is not interested in a finite conclusion, instead preferring the unshakably messy open-endedness of life outside the movie screen. The picture's last minute may anger those who prefer neat wrap-ups topped with a bow, but let them be mad. For everyone else who likes it when films leave the viewer with something to talk about while pondering its deeper implications, the closing moments are thrilling in their loaded ambiguity. Thematically dense and intelligently crafted, the darkly enthralling "Prisoners" will not easily be forgotten.