Here’s a movie you can’t get out of your head, a sci-fi horror story with the seductive allure of a classic romance. In filming Kazuo Ishiguro’s 2005 novel Never Let Me Go, director Mark Romanek (One Hour Photo) maintains the fragile mystery with a cinematic pull all his own. The children at Hailsham, a British boarding school, are being raised in what appears to be a parallel universe for a special mission they barely understand. One of them, Kathy, played with implosive grit and grace by the astonishing Carey Mulligan, narrates the tale, telling us what happens when she and her friends — Tommy (Andrew Garfield), whom Kathy loves, and Ruth (a quicksilver Keira Knightley), who steals him from her — join the others in the Cottages. I’ll say no more, except to praise the visual skill with which Romanek creates this world, the delicate power of Alex Garland’s screenplay, and the stellar performances. Garfield (the new Spider-Man) is mesmerizing. His scenes with Mulligan are heartbreakingly poignant. Ignore complaints that these lost children don’t earn our sympathy because they don’t rage against the machine that created them as expendables. Think instead of how many times you’ve resigned yourself to a skewed sense of duty promoted by others. The melancholy attached to the impermanence of life and love suffuses this film, making it memorably haunting and hypnotic.