George Lucas couldn’t do it; “The Empire Strikes Back” might have been superior to “A New Hope,” but “Return of the Jedi” was a dud. And the Wachowski brothers certainly didn’t manage the trick; “The Matrix” was good silly fun, but this year’s twin sequels were disasters. But Peter Jackson shows how it should be done. “The Two Towers” was an improvement on the already brilliant “The Fellowship of the Ring,” and now the third installment proves an eminently worthy follow-up to it. “The Return of the King” is a masterful conclusion to a magnificent series, and with it “The Lord of the Rings” becomes the cinematic trilogy against which all others must now be judged.

Taking up Tolkien’s tale where “The Two Towers” left off, the new installment follows the story to its logical conclusion by following several parallel narratives along their simultaneous paths. One centers on the trio of Aragorn (Viggo Mortensen), Legolas (Orlando Bloom) and Gimli (John Rhys-Davies) as they accompany King Theoden of Rohan (Bernard Hill), whose stronghold of Helm’s Deep was the site of the culminating battle of part two, to raise a force and go to the defense of Minas Tirith, the seat of the realm of Gondor now threatened by Sauron’s massive army. Tagging along with the warriors incognito are Theoden’s daughter Eowyn (Miranda Otto) and hobbit Merry (Dominic Monaghan). Meanwhile, the wizard Gandalf (Ian McKellen) goes ahead to Minas Tirith with Merry’s pal Pippin (Billy Boyd) to persuade the regent, Denethor (John Noble), to prepare for the enemy assault. Denethor, however, is nearly incapacitated by both the demise of his favorite son Boromir (Sean Bean) and the realization that he might be forced to give up power in favor of the returning Aragorn; and he callously sends his surviving son Faramir (David Wenham) to an almost certain death. In the end only Gandalf’s intervention will help Gondor survive until reinforcements arrive. Meanwhile, of course, the intrepid hobbits Frodo (Elijah Wood) and Sam (Sean Astin) continue their long trek to Mount Doom to destroy the ring and deny its power to Sauron, the awesomely evil all-seeing eye. Their journey would be a perilous one in any event, but it’s made much more so by the continued presence of the alternately helpful and treacherous Gollum (once again brilliantly rendered through CGI magic and the artistry of Andy Serkis), who seeks to stir up enmity between the two old friends. Ultimately the humans surviving the battle of Minas Tirith must face off against Sauron’s enormous forces once more to buy Frodo the time he needs to fulfill his mission. But the sinister power of the ring could still prove an insurmountable obstacle.

Jackson and his fellow screenwriters Fran Walsh and Philippa Boyens shuffle all these story strands together with complete confidence, and the director, aided immeasurably by editors Jamie Selkirk and Annie Collins, realizes the transitions on-screen beautifully while dropping in periodic nods to other characters not directly involved in them–Arwen (Liv Tyler), Galadriel (Cate Blanchett), Elrond (Hugo Weaving) and Bilbo (Ian Holm), among others. Their skill is perfectly complemented by the once-again astonishing work of the behind-the-scene crew. Andrew Lesnie’s ravishing cinematography catches the imposing beauty of the New Zealand locales, and the production design (Grant Major), art direction (Dan Hennah and associates), and costuming (Ngila Dickson and Richard Taylor) are all exemplary. And above all one must mention the spectacular success of the CGI team, which not only succeeds in rendering Gollum as a more fully realized character than the flesh-and-blood people in most other films but produces an amazing array of creatures, both earthbound and winged; a giant spider that confronts Frodo and Sam at one point is perhaps the most notable of them, but he has plenty of fine company. Again, the battle sequences are on a scale that beggars anything seen on screen before, and they’re staged with verve and precision, with individual feats of valor spotlighted in a way astutely designed to keep the adrenaline flowing. And after all the sturm und drang, Jackson pulls up at the end for a calming, blissful final reel, lovingly portraying the return of peaceful order after the ordeal of combat.

But, as in the previous installments, the brilliance of the technique on display would mean little if the film weren’t so emotionally involving, and the success in that regard is largely the result of the superb cast. Once again all the major players do yeoman work–McKellen brings wit and gravity to Gandalf, Mortensen is a stalwart hero, and doe-eyed Wood–even more than in the earlier films–makes the burden of Frodo’s quest palpable. Serkis not only gives life to Gollum, but gets to show us his progenitor, the human Smeagol, in a prologue that shows the origin of his obsession with the ring. Virtually everyone else is provided with at least one standout moment when he can take center stage and shine–the equivalent of a cadenza when he or she steps out from the chorus to strut his stuff–and they’re mostly very impressive. (Perhaps the most noteworthy is Legolas’ Big Moment on the battlefield, which Bloom and his CGI opponent both handle with aplomb and Rhys-Davies, as the admiring but gruff Gimli, follows up with a well-chosen quip.) But two figures emerge with special stature. One is Hill, whose turn as Theoden in “The Two Towers” was slightly disappointing but who comes into his own here, making the king a figure of true grandeur. And the other is Astin, whose eager, ordinary, utterly supportive Sam becomes in his unpretentious way perhaps the most heroic and affecting character of all. Singling out these two, however, shouldn’t minimize the contributions of the delightful Boyd and Monaghan, or of Otto, whose Eowyn is the very model of feminist courage and sacrifice. This is truly a group effort in which no one lets down the team, even if Noble can’t make Denethor any more palatable a figure than the dour, uncomprehending fellow is. (And one does miss Christopher Lee, whose oily villainy as Sauroman was such a joy in the first two films.)

If one wants to pick nits, he can note a few minor problems with “The Return of the King.” One is a difficulty carried over from previous installments–a tendency for tears to break out remarkably often. (This has got to be the weepiest group of action heroes ever committed to film–evidence, perhaps, of the less macho, more sensitive age in which we live.) Then there’s the embarrassment of climaxes at the close; indeed, there are so many false endings that one gets the feeling that Jackson just couldn’t bear to part with his cherished project. But we can understand how he felt, because even after nearly 200 minutes, we’re reluctant to see it end, too. And these are, in any event, mere quibbles in the face of a trio of films of astonishing vision and accomplishment. Jackson’s triumphant conclusion to his “Ring” cycle is so good, and his handling of the giant spider sequence in it so superb, that one is even moved to believe that his planned remake of “King Kong” will turn out well. If he can’t pull it off, no one can.