At the start of Mark Romanek’s slow-burning, achingly tragic adaptation of Kazuo Ishiguro’s novel Never Let Me Go, a few lines appear against a sky-blue screen, coolly informing that “the medical breakthroughs” happened in 1952, and that by 1967 average life expectancy had hit 100 years. We see the narrator, Kathy H. (Carey Mulligan), watching with resignation through a window as a man with a shaved head and a large scar is prepped for an operation. She talks about her being part of some special group which most people have incorrect preconceptions: “We aren’t machines. In the end, it wears you down.”

As you’re anticipating that end, the film cuts to the late 1970s, and a stately manor home in the English countryside that’s operating as a boarding school called Hailsham. The young Kathy (Isobel Meikle-Small) becomes friends with Tommy (Charlie Rowe), a quiet kid the others spurn because of his uncontrollable fits of rage, only to see her supposedly best friend Ruth (the terrifying Ella Purnell) snatch him from her. No matter the pain this causes Kathy, it doesn’t stop the three from from remaining friends until leaving Hailsham in the mid-1980s, after which they will have to confront a destiny already planned out for them. (It’s hinted at in the extreme care given to their health while at Hailsham, with medical checkups, a row of milk bottles and medications set out each morning, and brusque reminders of how “special” they are.)

While the complex triangle among these three forms the heart of Ishiguro’s narrowly focused novel, the precise screenplay by Alex Garland (The Beach) is filtered through Kathy’s perspective, specifically, her attempt to make a worthwhile life in this alternate England. This makes it easier to comprehend how she and Ruth are able to stay friends, despite Ruth’s near-constant meanness and status-seeking. The adaptation also takes in a little of the world around these children who both live apart from the mainstream of society, and yet are immeasurably important to it.

Ishiguro never answers the question as to why none of the children tries to break out of the system once they discover why they’re at Hailsham. Garland thinks to include a few hints of the boundaries imposed on them. An unprepossessing metal box at the door to their residences beeps red when they place their wrists against it when entering or exiting, as surveillance camera quietly tracks their activities. On their first visit to the “outside,” the teenaged Kathy, Tommy (Andrew Garfield), and Ruth (Keira Knightley) stare mutely at a chip shop menu, unable to comprehend what it is. This last is a particularly compact visualization of the children’s alienation, one never quite explicated by Ishiguro, and neatly conceived by Garland and Romanek.

As he showed in the slight but affecting One Hour Photo, Romanek (one of the few directors to come out of music videos who doesn’t make that background a badge of shame) seems adept at crafting unsettling drama in seemingly mundane surroundings. In Never Let Me Go, he refuses to play around with the physical trappings of science-fiction and offers only insinuations of the alternate history. All the backdrops (as well as clothes, cars, and signs) appear much as they would today, with the exception of the protagonists’ appearance, a melange of hand-me-down jumpers and carelessly shagged haircuts a decade or more out of date.

Helping Romanek along is the fact that the postwar British landscape, with its vaguely crumbled architecture, sense of privation, and air of gruff submission, lends itself all too easily to an atmosphere of unseen, assumed authoritarianism. A few wrong notes crop up in the script’s kid-gloves treatment of Kathy’s romantic yearnings (Ishiguro was more forthcoming about such things, and didn’t feel the need to craft an angelically asexual persona) and the muffling of a few key moments by the overuse of Rachel Portman’s heart-tugging score (which unfortunately scream out “quality literary adaptation”).

The best science fiction isn’t those stories that are most unnerving, but those most true. For all its invention, this is a story of familiar human truths, few of them welcome.