Judging by the adequacy of Indiana Jones & the Kingdom of the Crystal Skull, Indy shouldn't be put out to pasture just yet, but he's certainly not in Triple Crown shape. Actually, the nineteen years since Indiana Jones & the Last Crusade have taken their toll on the story-shaping skills of the creative team more than the hero's physical prowess or ability to extract himself from perilous situations.

A certain amount of humorous self-reference was integral to the first three pictures in the popular series. This entry feels hokey and jokey, mired in nostalgia and strewn with Spielbergian and Lucasian themes as fake as the cobwebs used on the sound-stagey sets. Instead of a taut narrative, there's a kitchen-sink approach to plotting that requires too much exegesis (think National Treasure) and results in a creaky cartoon effect. In a story containing many less-than-fresh referents and influences, Indy has close encounters with a cardboard Commie villainess (Cate Blanchett), an atom bomb, space aliens, Spanish conquistadors, his progeny, and an old flame.

It's as though director Steven Spielberg and producer George Lucas rummaged through their respective bodies of work to find themes to recycle. For Spielberg, it's patrimony and extraterrestrials. For Lucas, it's 1950's drag racing and the malt shop angst of American Graffiti. On the plus side, the long, digitized action sequences are exciting -- up-to-snuff if not innovative -- and there's enough spookiness to make an impression on younger viewers.

The period is the Cold War, when the Red Scare and an atmosphere of suspicion predominates at home and abroad. Russian KGB agents commanded by Stalin's favorite operative Irina Spalko (Cate Blanchett sporting a Cleopatra hairdo and rapier) have captured Indy and a British spy colleague Mac (Ray Winstone). At a military warehouse in the Nevada desert, they uncrate an otherworldly creature from the infamous Roswell site in New Mexico. Indy escapes but must shield himself from a nuclear blast that has dire fallout. The FBI starts snooping around and he resigns his university professorship.

On his way out of his quaint college town, he encounters Mutt Williams (Shia LaBeouf), a greaser on a motorcycle and the spitting image of Brando in The Wild One. Mutt asks Indy to help him find his godfather Oxley (John Hurt), one of Indiana's closest friends and a fellow archeologist, who claims to have found the crystal skull of the title. Mutt's mother has also gone missing. After a chase through the halls of academe, Indy and his newest sidekick head down to South America and promptly retrieve the skull. But Spalko and her goons are waiting with Oxley and Mutt's mom, who turns out to be Marion Ravenwood (Karen Allen) Indy's love interest from Raiders of the Lost Ark.

The movie's middle section takes place in the Amazonian jungle, with obvious and intermittently thrilling debts to both modern special effects and Tarzan flicks of yesteryear -- the latter including vine-swinging, giant waterfalls, and voracious red ants. In possession of the mysteriously powerful skull once again, the quintet of Jones, Mutt, Oxley, Marion, and Mac make their way to the fabled Mayan city of gold where the heavens open in a strained, faintly absurd climax.

The message seems to be that the unfettered, unprincipled quest for knowledge can be dangerous and you have to know when enough is enough. One sign this franchise may have reached that point -- and doesn't really believe in itself anymore -- is how the revelation of Mutt's provenance is played for dumb laughs. The humor is lacking, much as the attempt to rekindle a romance between Indy and Marion feels perfunctory, their initial bickering annoying, and the overall story random.

Expectations may be unfairly high, but Crystal Skull's problems aren't simply relative to the first three movies or evident in comparisons with similar pictures made in the interim. Retro lighting is supposed to evoke noirish romantic adventures and Saturday afternoon serials, yet signals plodding self-parody by exposing how artificial the enterprise looks and feels. John Williams' famous theme and incidental scoring sounds dated, enhancing the sense of fatigue.

Returning to the thoroughbred metaphor, high stud fees are all our aging hero can expect to win going forward. That is, unless Spielberg and Lucas -- experts at keeping lucrative franchises alive -- can fashion a narrative for Mutt/Shia LaBeouf that a third generation of Indy fans will find compelling and fit for the winner's circle. Don't count them out.

(Released by Paramount Pictures and rated "PG-13" for adventure violence and scary images.)