'Never Let Me Go,' a sci-fi flashback

The more believable a scenario, it seems, the more affecting the horror, which was certainly the case with "Never Let Me Go," the 2005 novel by Kasuo Ishiguro ("The Remains of the Day"), now a disturbing, haunting film directed by music video-maestro-cum-feature-director Mark Romanek.

Starring three of Britain's better young actors (Carey Mulligan, Keira Knightley, Andrew Garfield), it offers up a world that didn't happen but might have - and still could. Considering how subtly Romanek's movie gives up its secrets, it would be unkind to provide too much explanation here, so if you want to stop reading, do so with the assurance that the movie is enormously rewarding, and probably unforgettable.

If not . . . "Never Let Me Go" is set in a world that sci-fi rarely visits - the past: It's 1978, and yet the English boarding school we see seems wrapped in wartime austerity, woven out of wet brown wool, adorned with cracked pottery. On shopping day, the children redeem their hard-won tokens for broken toys and castoffs. And they are castoffs themselves: Kathy, Ruth and Tommy (Mulligan, Knightley, Garfield) are all part of an underclass that has been bred to provide donor organs for the regular population: The curing of the previously incurable has required the creation of humans as spare parts.

The characters' realization of what this means, and how they can live with it (or not), is what Romanek and his cast articulate so artfully.

The genius of Ishiguro's story was in turning the slightly fantastic into simple parable: The meaning of life is no mystery to Kathy, Ruth and Tommy; they were bred for a very specific reason. And what makes them so very different from the people they were born to save? Not much, which is part of what makes "Never Let Me Go" so memorable, and awful.