Even on its own, "The Lord of the Rings: The Return of the King" is a rousing action movie. But viewed for what it truly is, it is probably one of the greatest third acts in cinema history.

Photo © Copyright New Line Cinema Ian McKellen stars in the third installment of ''The Lord of the Kings.''

Credit director Peter Jackson for being crazy enough and skillful enough to bring J.R.R. Tolkien's trilogy to the screen, and credit the executives at New Line Cinema for betting more than $300 million and their studio's future on Jackson's madness.

As with the second installment, Jackson throws the audience right into the thick of it, starting with a chilling flashback that shows how Smeagol (Andy Serkis) found the One Ring and slowly became the sad, obsessed creature called Gollum. Then Jackson shifts to the present, as most of the Fellowship's surviving members reunite at the ruins of Isengard. Although the treacherous wizard Saurman (Christopher Lee, whose scenes were cut from the third film) has been defeated, the greater threat remains. Saron and his armies are ready to move against the human kingdom of Gondor.

Gandalf (Ian McKellen) and Aragorn (Viggo Mortensen) race to raise an army to defend Gondor's capital city, Minas Tirith. But, as before, mankind's fate ultimately rests with two tired hobbits, Frodo and Sam, who are slowly making their way through enemy territory, inching toward Mount Doom, the one place where they can destroy the One Ring and with it Saron's power.

Like the final act of any good epic, "The Return of the King" movies briskly. It is all action and resolution. And if it has a flaw, it is that McKellen and Mortensen don't have much to do except rally armies with speeches cribbed from "Henry V."

That leaves Sean Astin's Samwise Gamgee to steal the show, much as Serkis' computer-assisted Gollum steals "The Two Towers." Astin's performance is touching, powerful and always pitch perfect. After playing sidekick to Frodo Baggins (Elijah Wood) for two films, Sam gets to shine here, especially in his fight with the giant spider, Shelob.

The Battle of Minas Tirith is a special effects showcase, featuring flying dragons, larger-than-life elephants decked out as war machines and an army of 10,000 or more orcs. And once again Jackson treats us to the comic interplay between the Gimli (John Rhys-Davies) and Legolas (Orlando Bloom) as they try to one-up each other in battle. (Memo to George Lucas: If you must have comedy during a battle sequence, this is how it is done.)

Tolkien purists, of course, will find plenty of things to nitpick. Jackson has made more changes in adapting "The Return of the King" than he did in adapting the other two novels. For instance, in the books Sam's fight with Shelob takes place at the end of "The Two Towers," but Jackson moves it to near the end of the third film. And, more controversially, Jackson jettisons most of the anticlimactic events that occur in the last half of Tolkien's concluding novel. Even still, it takes Jackson about a half an hour to wrap things up following the film's climactic battle.

To the purists I say, get over it. Jackson has remained true to the spirit of "The Lord of the Rings" if not the letter, which is more than anyone else could have done.

After all, everyone else thought Jackson was crazy.