Indiana Jones and the Kingdom of the Crystal Skull (12A)

A tomb raider returns

The fourth, and surely final, instalment of the Indiana Jones series begins with a great rollicking blast of "Hound Dog" and an open-top Cadillac bouncing along with bobbysoxers. It's intended to convey the exuberance of being young, hip and American. Some minutes later, we get our first look at the hero of the hour, and while he's undeniably American, there is little that is youthful or hip about Indiana Jones. The lined, craggy face and grey hair tell the story: he ain't nothin' but an Old Dog, and new tricks aren't his thing.

Going in to the film, one nevertheless feels a surge of goodwill towards Indy, perhaps because he represents the last gasp of a fond tradition – the plain, meat-and-potatoes heroism of the Saturday-morning serial. Harrison Ford, at 65, retains the stolid virility of a Gary Cooper, and if he's not quite so nimble on his feet, his willingness to go one final round is enough in itself to get us onside. Ford has always been a limited actor, but what he provides within those limits – a gruff male humour, a narrow-eyed watchfulness, a touch of fear – has answered magnificently to whatever the part needs, be it troubled men (Witness, Blade Runner), wronged men (The Fugitive) or just President of the USA (Air Force One).

The really tough job here belongs to Steven Spielberg, who hasn't made an Indy movie in nearly 20 years (Indiana Jones and The Last Crusade came out in 1989) and will have seen how much the action field has changed in the interim. The Bourne trilogy, in particular, has set a standard of pace and energy that makes competitors much younger than Spielberg look a bit sluggish. If The Bourne Ultimatum is a shot of superstrong double espresso, The Kingdom of The Crystal Skull is a mug of Ovaltine, and the temptation to watch it with a tartan rug over your knees may prove irresistible.

Set in 1957, the film glimmers with Cold War paranoia, and Indy's enemies are no longer the Nazis but the Soviets. An American military base is hijacked by a unit of Russian stormtroopers, led by "Stalin's favourite scientist" Irina Spalko – Cate Blanchett plays her with a Louise Brooks bob and a Rosa Klebb accent – whose mission is to return a legendary crystal skull to its home. Why? Oh, because it will yield the secret of all knowledge and grant the USSR world domination, or something; more importantly, it will require a journey deep into the jungles of Peru, where catacombs, cobwebs and cadavers are absolutely guaranteed.

Before the film decamps there, Spielberg does pull off one terrific set-piece. Indy, having escaped Spalko and her goons, finds himself in a picture-perfect town that reveals itself to be a model for a nuclear testing facility, with mannequin families spookily inhabiting the rooms. Then, a 30-second warning blares forth, and Indy rushes into a house in a search for cover against the blast. His choice of refuge: a family-sized refrigerator. Cool! There follows a moment of hushed awe as Indy walks out into the obliterated landscape and watches the mushroom cloud go up. It's as if the movie is waving goodbye to its own innocence.

After this spectacular, however, the thrills come thin and slow. Indy picks up an adventurer named Mutt (Shia LaBeouf), a brattish James Dean-type to replace his perfidious sidekick, Mac (Ray Winstone). It transpires that Mutt's mom is one of Indy's old sparring partners, Marion from Raiders of the Lost Ark. While it's good to see Karen Allen return to the series, it's mystifying that the script gives her nothing to do.

But then, screenwriter David Koepp is either filling out the lines with dreary stuff about 16th-century conquistadors or sitting back while Spielberg whips the action sequences into a frenzy. One chase sequence seems to last about 20 minutes, during which the stuntmen do a lot of work without contributing the smallest degree of excitement. Later, there's a trip down the Amazon involving no fewer than three vertiginous drops over a waterfall, each one more tumultuous than the last, but actually no more terrifying.

That could be almost emblematic of the film's problem: it keeps getting bigger without getting better. And Koepp isn't entirely to blame. When the plot veers into the extraterrestrial, and wizened creatures pop up like those molten furies at the end of Raiders, you recall that the story is credited to producer George Lucas, who can always be relied upon for a dose of scientific mumbo-jumbo. His mouthpiece here is a brain-damaged professor, played by John Hurt as a cross between Catweazle and Dennis Hopper's babbling fool in Apocalypse Now.

Indiana Jones and The Kingdom of the Crystal Skull is, like its title, long, daft and ungainly without ever becoming an object of contempt. Spielberg takes too much pride in his craft to let a movie run away from him, and he gets enough out of Ford and the rest to ensure that it will please the crowds. But those crowds are also bound to feel an acute sense of déjà vu. As Indy himself sighs at one juncture, "Same old, same old."

The antidote to this, I think, would have been a keener sense of comedy. I liked the moment when Mutt speculates on Indy's age – "Eighty or something?" – and the opening visual joke of segueing from the Paramount logo to a molehill. Just occasionally, you remember why you liked this stuff in the first place. The rest of the time, it just looks like Indy's battered brown fedora: old hat.