This visually attractive adaptation of Kazuo Ishiguro’s novel is like a didactic episode of “The Twilight Zone” told in slow-motion. Director Mark Romanek employs extreme deliberation, high-toned cinematography (by Adam Kimmel), a mournfully elegiac score (by Rachel Portman) and a cast of soulful young actors to turn what’s essentially pulp material into an artsy, pretentious tearjerker. Think “Logan’s Run” told in the style of “Gattaca” and you’ll have some idea of what to expect—something like “Logan’s Maudlin Stroll.”

The initial reel of the film, set in 1978 at an English boarding school called Hailsham, is both affecting and mysterious. The staff, headed by stern headmistress Miss Emily (Charlotte Rampling), oversees a brood of sweet young boys and girls with a strong hand, demanding both that they be obedient and that they keep themselves healthy. The children are first observed through the eyes of new teacher Miss Lucy (Sally Hawkins), who’s taken aback by some of the school’s administrative methods. (The students are kept from leaving the grounds, for instance, by horror stories about children who disobeyed and were gruesomely killed beyond the gates.) And the youngsters—including the three who become the focus, Kathy (Isobel Meikle-Small), Ruth (Ella Purnell) and Tommy (Charlie Rowe)—are slightly strange and otherworldly. At first you think that they might be orphans, and that their peculiarity is the result of the loveless way in which they’ve been raised.

But roughly thirty minutes in, we learn the truth through Miss Lucy, who ends her career at the school by telling her class who they really are: (And if you don’t want to know, you should stop reading here.) They’re clones, raised to serve as organ donors in a national program used to extend life for citizens to incredible lengths. But that doesn’t mean that they lack emotion. That’s clear from the story of the lead trio. Kathy develops a crush on troubled Tommy, who shyly reciprocates by using his “tokens,” which they earn for good conduct, to buy her a cassette tape (featuring the song that becomes the film’s title) from the second-hand stuff occasionally delivered to the campus. But Ruth, though Kathy’s best friend, intervenes to steal him away. Kathy is understandably morose.

Still, the three remain friends until their removal as young adults (Kathy now played by Carey Mulligan, Ruth by Keira Knightley and Tommy by Andrew Garfield) from Hailsham to the Cottages, a sort of rustic way station where they await assignment. During their stay there Kathy decides to volunteer as a Carer, who tends to Donors after their surgeries, until she will become a donor herself. That separates her from Tommy and Ruth, though she will find them again later, after they’ve already begun the donation process. It’s at this point that Ruth tries to make amends for her betrayal of Kathy by suggesting that she and Tommy seek a rumored escape clause allows any clone couples who truly love one another a few years’ respite before having to fulfill their donor requirement.

But even the fragile happy ending such a reprieve would bring isn’t what “Never Let Me Go” is all about, of course. Romanek wants to use the pulpy premise—the sort of great silly sci-fi idea that animates such classics as “Fahrenheit 451,” but doesn’t bear much logical scrutiny—to extract tears (which he does often from his cast, especially Mulligan, and will undoubtedly manage to do from many viewers as well). But like Ishiguro, he and scripter Alex Garland also want to raise questions about the ethics of such medical practices as the ones imagined here, as well as broader philosophical (or quasi-theological) concerns—would clones have souls, for example? And as the final scenes too heavily emphasize, the issues these characters face are actually relevant to all us uncloned people, too.

As played out here, though, those sorts of higher matters play a distinct second fiddle to the romantic triangle, which actually has a very old-fashioned tone. Kathy and Ruth are like many female pairings from Hollywood’s heyday, with the one restrained, self-contained and long-suffering and the other reckless, selfish and cruel. Mulligan and Knightley play them in a fairly standard way, too, with the former like Olivia de Havilland to the latter’s Vivien Leigh; they’re both fine, but the roles don’t tax them overmuch. As the boy torn between them, Garfield evinces the kind of stuttering vulnerability that’s reminiscent of Montgomery Clift or Anthony Perkins (whom the actor distinctly resembles, especially in a woodland scene with Mulligan at the Cottages). The children who play their younger selves are fine, with Meikle-Small a standout, and Rampling is her usual authoritative self as the imperious headmistress. Her likeness to a haughty Lauren Bacall has never been more evident.

So while impeccably made, with many shots as evocative as paintings and a talented young cast doing its best, “Never Let Me Go” fails to elevate what’s essentially a mawkish romantic triangle through its sci-fi trappings and philosophical posturing. Contrary to the film’s whole purpose, its characters never emerge as fully human, and what it ultimately says about the human condition turns out to be rather banal. Like so many tales of this kind, it’s just too solemn and serious for its own good.