Never Let Me Go is sci-fi for the Belle & Sebastian set.

A beautifully mopey adaptation of Kazuo Ishiguro's much-praised novel, with Keira Knightley, Carey Mulligan, and Andrew Garfield as young Brits in dark mood and rumpled mode, the film offers a meditation on identity, repressed longing, existential dread, and organ farming - in a seemingly idyllic England of the late 1970s and then into the 1980s.

Seemingly, of course, is the operative word. As children living at the cloistered Hailsham School (there are juvenile doppelgängers in the roles later assumed by the three stars), Ruth, Kathy, and Tommy are led to believe they are something special: To maintain their bodies in salutary condition is a high priority, as the headmistress (Charlotte Rampling) and her faculty emphasize. But art, too, is encouraged. And the grounds of the school, with its verdant lawns and cricket pitches, feel like an exceptional place.

Exceptional, but also strange.

If you haven't read Ishiguro's book, or read about it, or seen the trailer for Never Let Me Go, it might take a while to figure out exactly what's going on with Ruth, Kathy, Tommy, and their Hailsham mates. The nature of who they are, and why they are, is revealed in modest increments: that scanner by the front door that the students must brush their wrists across as they come and go; the mysterious deliveries of secondhand toys and games; the quick exit of a teacher (Sally Hawkins) too forthright in her talks with the children.

And then Ruth, Kathy, and Tommy are children no more, but young adults sent to live in "the Cottages" - a rustic encampment where they pass the time between visits to . . . the hospital. Ruth and Tommy become a pair, but it is clear from the wistful looks that Kathy throws Tommy, and Tommy her, that the wrong two have partnered.

All three are very sharp here: Knightley, dark-haired and deliberate, brings nuance and humor to what could have been a brittle role. Garfield, with the look of a scared rabbit in his eyes, casts a sweet and sensitive aura, a shaggy, gawky figure with an artist's soul. And Mulligan, who provides the film's spare, rueful voice-overs, barely gets through the scenes without bursting into tears. But that's being unfair: Although the actress' Kathy seems on the brink of crying, it's a tamped-down and delicate performance, really.

Alex Garland, the screenwriter and novelist (28 Days Later . . ., The Beach), and Mark Romanek, the director (One Hour Photo), have created an alternate universe that exudes some of the creepy calm of Wolf Rilla's great English science-fiction flick Village of the Damned, but also the gloomy romanticism of Keats and Shelley.

With its mix of Masterpiece Theatre Britain (thatched and hedgerowed villages, misty seaside towns) and modernist institutional architecture, the landscapes our ill-fated threesome tread are full of sullen allure. Let's go off and have a big sulk, they say.EndText