Spawning salmon have a tough task, swimming upstream and all that. Alfred Jones, the fisheries expert at the center of "Salmon Fishing in the Yemen," faces similar challenges. Though he's played by the effortlessly charming Ewan McGregor, Jones is a fuddy duddy nearly as cold-blooded as the fish he studies.

His relationship with his wife, a brusque finance expert, is more a matter of comfortable routine than conjugal bliss. "That should do you for a while," she says when they make perfunctory love. Fred is like one of P.G. Wodehouse's characters, overmatched by life. "I don't know anyone who goes to church anymore," he says wistfully. "On Sundays we go to Target."

Making this young fogey a viable romantic figure is the film's challenge. Luckily, there is a clever screenwriter ("Slumdog Millionaire" Oscar winner Simon Beaufoy), a warm-spirited director ("Chocolat's" Lasse Hallström) and a fetching co-star (Emily Blunt) to lend a hand.

Fred's slow thaw isn't as joyous as the change of heart that strikes priggish scientist Cary Grant in "Bringing Up Baby," but it's agreeable nonetheless. He is netted out of his government desk job by a bizarre research request. A sheik wants to stock the Yemen River with North Atlantic salmon. The government, desperate for a positive human interest news story out of the Middle East, appoints Fred to the task.

He is aghast. The idea is "theoretically possible," he says, "the way a manned mission to Mars is theoretically possible." Fred takes no solace in working alongside the sheik's attaché, Harriet (Blunt), a lovely English rose with soulful eyes and a snippy sense of humor. For her part, she wonders whether Fred has Asperger's. But under the desert sun, a romance that looks fundamentally unfeasible becomes theoretically possible.

There are clever ideas in the film, like Fred's heart-to-heart talks with the koi imprisoned in his back-yard pond. And some secondary characters are so vivid you wish they'd get a spinoff film of their own.

Kristin Scott Thomas proves herself a grand comedienne as the prime minister's press secretary who hatches the scheme, a tart, caustic conniver of imperial self-confidence. She is the sort of woman who could pick up her phone and have a hurricane canceled. She may be the scariest, funniest, most nuanced comic villainess since Meryl Streep wore Prada.

While "Salmon Fishing" fritters away the comic momentum of its madcap opening chapters, it's like angling -- a pleasant diversion if you can look below the surface and muster the patience to appreciate it.