Peter Jackson’s adaptation of J. R. R. Tolkien’s epic fantasy trilogy reaches its conclusion with Lord of the Rings: The Return of the King, and it’s doubtful that any viewer will be disappointed. In the last stages of the war to preserve the human race from the forces of Sauron, Tolkien’s warrior heroes, led by the king without a throne, Aragorn (Viggo Mortensen), hold the field. Meanwhile, the courageous halflings Frodo (Elijah Wood) and Sam (Sean Astin) creep behind Sauron’s unsleeping eye toward the fires of Mount Doom, where the ring Sauron needs to seal his power was forged and where Frodo, the reluctant ring bearer, must destroy it. The film is a majestic finish to what may be the greatest sustained piece of entertainment in the history of movies, and the most emotionally rich.

The struggle between good and evil was never less reductively shown. Jackson and his ingenious co-screenwriters, Fran Walsh and Philippa Boyens, begin part three in the least likely place: a flashback to the day Smeagol (Andy Serkis), once living peacefully among the river folk, became a murderer, strangling his brother over a glittering ring that they pulled out of the river mud. In Tolkien’s world the ring is the instrument of evil; humans are inherently weak and corruptible, susceptible to greed and lust for power, but not inherently bad. And the fairy-tale phrase “pure of heart” means nothing in a realm where everyone is liable to temptation; where actions, not character, are pure; and where the moral battle is fought not just on the grand scale by Aragorn’s army but on a smaller one by every individual.

Jackson makes us understand that the heroes’ surmounting of impossible obstacles is a symbolic representation of the eternal fight to hold onto our humanity. Smeagol loses his and becomes Gollum, his life unnaturally prolonged by his parasitic attachment to the ring, his form shrunken and reptilian. But there’s still enough of Smeagol left for Frodo to see through his treachery and to pity him. Serkis plays the character as a dual personality, half Smeagol, half Gollum; the Gollum voice that urges him to turn on his hobbit master, whom he guides through the mountains toward Sauron’s ghostly kingdom of Mordor, home of Mount Doom, is a personification of the evil of the ring.

The marvel of the first film in the trilogy, The Fellowship of the Ring, is the way Jackson advances the narrative through a seemingly endless visual variety—a new world every 15 minutes, as one friend expressed it to me. The Two Towers, racing at an almost alarming speed, is built around an extended battle sequence that rivals the fantastical wars that directors like Fritz Lang and Akira Kurosawa invented. The Return of the King feels like a series of valedictories, and that’s largely why it’s so overwhelming emotionally.

Another reason is that it’s the culmination of all the elements set in motion in The Fellowship, and it concludes what turn out to be immense and extraordinary arcs in the performances of such actors as Mortensen, Wood, Astin, Ian McKellen (as Gandalf), Bernard Hill (as King Theoden), Miranda Otto (as his niece Eowyn), Billy Boyd and Dominic Monaghan (as Frodo and Sam’s hobbit pals, Pippin and Merry). We get to see Aragorn rise to Shakespearean heights: Mortensen’s finest scene is an eve-of-battle speech to his troops that was clearly inspired by Henry V’s St. Crispin’s Day tribute to the wartime virtue of camaraderie. We see Theoden, roused by Gandalf in The Two Towers from his enchanted lethargy to reclaim his purloined throne, in contrast to another king, Denethor (John Noble). Denethor continuously chooses territory and self over humanity, and his mourning for the battle-fallen son he once rejected becomes an embrace of death, whereas Theoden’s grief for his own son lights his way back to the world.

If the final movie belongs to any single actor, it’s Astin as Samwise Gamgee. Like Frodo, whom he follows literally to the edge of the fire and beyond, Sam discovers resources within himself that he never dreamed existed. And Astin the actor seems to grow in proportion to Sam’s character, as if he, too, were carried beyond his own limits.