“We’re good and lost now,” says Barbossa with satisfaction. “For certain you have to be lost, to find a place as can’t be found. Elseways, everyone would know where it was.”

What he had in mind was the otherworldly realm beyond the world’s end, but Barbossa might as well be describing that almost equally unattainable holy grail of popcorn franchises: a worthy third chapter to a trilogy.

The shoals of Hollywood history are cluttered with the wrecks of “threequels” that fell short of their predecessors: Superman III. Batman Forever. X-Men 3. Shrek the Third. And so on.

Give the filmmakers credit. They were willing to get good and lost. To sail into uncharted waters, to do something new, rather than play it safe by repeating what had been done before. To go to the ends of the earth, to take risks even bigger than the ones that made last summer’s Pirates of the Caribbean: Dead Man’s Chest one of the best popcorn movies in ages.

Alas. They got good and lost, and never found their way again. If Dead Man’s Chest was inspiration gone amok, Pirates of the Caribbean: At World’s End is more — much, much, much more — of the same, only without the inspiration. In every respect it outdoes its predecessor, except in charm, entertainment and fun. Add Pirates of the Caribbean to the roster of franchises foundering on the rocks the third time out.

Johnny Depp still reels and prances as Jack Sparrow, but the character’s appeal has always lay in the fact that he was as much a con artist as a pirate, with a peculiar blend of quirky brilliance and shameless self-promotion. Till now he’s been able to keep just a half-step ahead of everyone else, subtly manipulating events to his own advantage, all the while impudently flirting with Elizabeth Swann (Keira Knightley) and slyly goading Will Turner (Orlando Bloom).

All of that is gone here. Barbossa (Geoffrey Rush), Will, Elizabeth and the Caribbean witch Tia Dalma (Naomie Harris) succeed in their mission to ferry back Sparrow from Davy Jones’ Locker. But Jack is a shadow of his former self, a dazed and confused prisoner of a plot he understands no better than we, mumbling to computer-composited replicas of himself in a feeble conceit that is technically expensive, surely, but dramatically cheap.

If Jack Sparrow was the series’ Han Solo figure, Will and Elizabeth have been the Luke and Leia figures: the lowly but valiant young hero, the feisty action princess. Now they’re more like the Anakin and Amidala. They’ve got far too much angst and self-seriousness, and no time amid the plot machinations for the lighthearted chemistry of the earlier films.

Then there’s Davy Jones (Bill Nighy), the most stunning and memorable special-effects villain since Return of the Jedi’s Jabba the Hutt. Here, pressed into the service of the East India Company by the nefarious Lord Cutler Beckett (Tom Hollander), Jones’ formidable presence is incalculably diminished. Showing little of the aura of barely restrained menace he should have had even under these circumstances, Davy’s a patsy.

So much promise unfulfilled, so many setups leading only to letdowns. Consider the last film’s cliffhanger return of Barbossa, whose brilliantly orchestrated death was the climax of the original Curse of the Black Pearl. When he made his electric reappearance in the final seconds of Dead Man’s Chest, Tia Dalma explained that the journey to world’s end and beyond to bring back Jack Sparrow from the dead required the guidance of one who “knew those waters.”

The implication was that Barbossa, having himself returned from the dead, was uniquely qualified to lead the journey to bring back Jack. At the very least, the story behind Barbossa’s return should have been something comparable to the convoluted and satisfying way that he died — and as Jack’s return ought to be.

No such luck. All we learn about Barbossa’s return is that Dalma brought him back to life. Period. Of his “experience in those waters” we learn nothing — except that it has nothing to do with his having returned from the dead or with his qualifications for bringing back Jack. Given how spectacularly staged Barbossa’s death was, this deus ex machina return is a major disappointment.

Then there’s Davy Jones, who is given a tragic romantic back story, and even a poignant scene with his lost love. This could have been the stuff of grandly mythic romantic nonsense, but instead it just peters out as both characters drop out of the story. There’s no real sense of closure or character arc.

At World’s End so vastly expands the scope of the Pirates universe that a summary is an almost futile gesture. Would you believe that Jack and Barbossa are two of nine piratical potentates in a hitherto unknown privateer ruling body called the Brethren Lords of the Pirate Court, which once conspired with the malicious, heartbroken Davy Jones to imprison Jones’ tempestuous, unpredictable lover, the sea goddess Calypso, in human form? Whew.

So much has the mythology grown and metastasized that, rather than providing context for the characters and the story, it now dominates and overshadows them. This is remarkably similar to what happened in the Star Wars prequels and the Matrix sequels. Perhaps it would be helpful to have a term for this phenomenon: Over time, franchises tend to become mythology-bound.

As the film spirals into chaos, one recurring line sums up At World’s End as well as anything. Toward the end, as Cutler Beckett walks almost serenely amid explosive destruction in a veritable sea of flying debris, he says matter-of-factly, and not for the first time, “It’s just good business.” Maybe director Gore Verbinski felt the same way.

Steven D. Greydanus is editor and chief critic of DecentFilms.com

Content advisory:
Much stylized swashbuckling action violence and menace; repeated imagery of mass hangings, including the hanging of a child; some gross-out imagery and humor; mild sensuality and innuendo; a briefly violent “romantic” advance on a woman; a depiction of a soothsayer/witch and a pagan sea goddess.