There’s something about Jake Gyllenhaal that just doesn’t do it for me as an action hero. Maybe it’s those puppy dog eyes, his dim-witted expressions, that boyish charm – he fires soft and sensitive in every direction, even when script and settings call for Harrison Ford’s ironic virility. In Prince of Persia: The Sands of Time, Gyllenhaal is the one glaring miscast as Dastan, the Prince of Persia, who is a cross between Sinbad, Ali Baba, and Indiana Jones.

It seems the thought here is that since Dastan is a street urchin picked off the street to become an adopted son of the king, Gyllenhaal’s rounded good looks and soft features will make those humble origins stick to the character – set him apart from the chisel-faced Lord of the Rings extras who play the rolls of the royal family. But Gyllenhaal seems uncomfortable as an action hero. He reacts to action and combat with awkward grunts and groans, and the actor’s unconvincing performances in front of the green screen (computer generated wizardry orchestrates the film’s climax) makes it look like he was woken up in his trailer and thrust on camera after the stuntmen finished their takes. The script demands the kind of action hero that grabs his adventure by the cojones, but we get one who fumbles his way to its conclusion. It a key missing piece in a film that otherwise could have been a successful, Raiders of the Lost Ark meets The Mummy adventure story.

Other roles are more than adequately filled. A chilly Ben Kingsley plays Nizam, the Persian king’s brother, who lobbies for the invasion of the holy city of Alamut in order to steal a magic dagger that has the power to turn back time. Nizam wants to return to a moment in his own childhood when he saved his brother’s life so that he can let his brother die and enjoy a lifetime as king.

Opposite Dastan, Gemma Arterton is Tamina, the priestess-princess of Alamut, who is charged with protecting the dagger. When it lands in Dastan’s hands, Nizam frames the young prince for the murder of his father forcing Dastan and Tamina into exile together. Tamina more or less carries the film from this point out, turning the long scenes of traipsing through the desert into sparkling conversations fired with spunky, quick-witted, and sharp-tongued dialogue. Arterton seems to be reaching back to those great friction romances of the Hollywood Golden Age for inspiration – Clark Gable and Claudette Colbert in It Happened One Night; Humphrey Bogart and Katharine Hepburn in The African Queen – and she lifts this boyish adventure story above the rigmarole of connecting the plot points and action sequences.

Another bright spot is Alfred Molina as the shifty and jovial ostrich race promoter Sheik Amar. The Sheik offers a cartoonish sideshow to a movie that is otherwise a stilly story about magic knives and nonsensical time travel (it is based on a video game, after all). Molina’s humor helps balance the whole thing out.

The film concludes in a great series of explosions, sand flows and other of the now usual over-the-top computer gadgetry that gets less exciting to watch with each passing year. It is a shame more directors don’t opt to go back to the Universal Studio-style models, foam, and perspective play that made the adventure stories of yesteryears less huge but more convincing. Still, while the world of the Prince of Persia almost falls apart, the movie never does. The key ingredients here are Arterton, Molina, and Kinglsey, who add the spunk, sex, humor, and dread to keep this adventure story flowing with interest.