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Clone love is the equally slow-moving subject of Never Let Me Go, a sci-fi romance based on a Kazuo Ishiguro novel whose story starts in 1978 but, interestingly, in a world whose technology exceeds our own. A medical breakthrough occurred in 1952, we’re told, and by the late ’60s, life expectancy passed 100 years. In 1994, we meet Kathy H. (Carey Mulligan), a “carer” whose exact responsibilities aren’t yet clear. Yet she teases that carers “aren’t machines…[the job] always wears you down.”

Back in 1978, though, Kathy was a student at Hailsham, an English boarding school whose students, the headmistress tells them, are “special” and must keep healthy. The kids are relatively carefree—except for worrying about those rumors of awful things that happen to children who leave the grounds—and normal, if a bit stressed by the school’s emphasis on art. Like any adolescents, then, they develop crushes: Kathy (now played by Isobel Meikle-Small) has a thing for Tommy (Charlie Rowe), an outcast with a bit of a behavior problem and an inability to get his drawings noticed. Kathy’s best friend, Ruth (Ella Purnell), doesn’t seem to care about Kathy and Tommy’s friendship, except when she does. By the time they’re young adults and ready to leave their first school for another, Ruth (Keira Knightley, with unfortunate bangs) has snagged Tommy (Andrew Garfield) for herself. Mulligan’s Kathy pines politely.

The heartbreak would perhaps be easier to bear had a “subversive” and quickly dismissed teacher (Sally Hawkins) not told the children the truth about their futures: Basically, that they had none, and were only bred to provide organs for the fatally ill. After a few donations, most of them would “complete”—Ishiguro’s prettier term for “die.” (28 Days Later… scripter Alex Garland adapted the book; One Hour Photo’s Mark Romanek directs.)

The majority of Never Let Me Go focuses on the love triangle, to snoozy effect. Kathy’s choice to become a carer gives her, essentially, a stay of execution, though the price is watching her peers die. Not much happens a decade before this, where the film lingers for a while, with the threesome making (or, in Kathy’s case, not making) friends, looking (not very hard) for their “originals,” and hearing too-good-to-be-true tales of the possibility of donor-deferment should a couple prove that they’re in love.

It all takes place in a gray, rainy, wool-sweater milieu; Adam Kimmel’s cinematography may echo the story’s somber tone, but doesn’t do much to keep the viewer from drifting. Neither does the acting: Mulligan, while lovely, isn’t given much to do but observe the others with her trademark parted-lips stare, while Knightely is noteworthy only for how scrawny and awful she looks. Garfield—the future Spider-Man—is also vanilla, his grown-up Tommy far less personable than the child.

The friends’ fortunes turn 10 years later, and finally the story turns its attention from romance to the more interesting ethical questions about the characters’ existence. With their ability to love, play, hurt, and create, are they worth any less than the people they’re saving? But such thoughtfulness comes too late. For a more engaging meditation on the wonders —and possible horrors—of science, read the book.