"Enduring Love" sounds a little like the sort of movie kids used to call "mushy": goo-gooing, smooching, squeezing, all that icky wet stuff. But they don't come any drier than this tough, taut little thriller, which is singular not only in its situation but also in its ideas. It's the best kind of movie: so alive in its storytelling that only in retrospect do you realize that the ideas represent a metaphysical inquiry.

And that is: What do we owe each other? Enduring love? A sporting try? Or nothing at all?

Of the four men asked that question one sunny afternoon in England, only one answers enduring love. For his pains, he ends up smashed in a field, in the grotesque posture of a fool who fell from the sky. The sensible chaps all bailed -- literally -- and now they've got to deal with that, each in his own way.

Such a situation could only come from the twisted but brilliant imagination of a major novelist, and few will deny that the Englishman Ian McEwan is one. But the metaphor he's constructed -- you won't even notice it's a metaphor -- is brilliant for its penetration of these issues.

The film is directed by Roger Michell (he of the excellent "Notting Hill"), and its opening scene finds an intellectual, proud of his hard-nosed rationalism, sitting with his lover in a field. He's about to propose, although it violates his principles: He believes love is merely a chemical disguise for an animal-brain mandate to replicate DNA. But from far off come cries for help. A lone fellow is trying to control a hot-air balloon in whose basket hangs a scared little boy. Our smart guy -- his name is Joe Rose and he's played by Daniel Craig -- runs to help, as do three others who seemingly come from nowhere. Each of the four gets a sound grip on the rope secured to the bouncing, crazed vehicle. But the balloon catches a breeze and springs aloft, bearing the boy with it. Joe and the others hang on. The balloon shoots skyward.

The balloon, I'm guessing, is the hot-air illusion of civilization, or nation or community. Fragile, dangerous, somehow necessary, it demands faith, even courage, to sustain. And so the dilemma: What do we owe the boy who stands for all the humans dependent upon those entities? Three of the men, Joe included, decide in a trice: not much. They opt for the old Every Man for Himself bit, and let go; with each abandonment the balloon shoots higher. The fourth man clings to the rope -- and the illusion. Up, up and away in a beautiful balloon of death he goes, until his fingers wear out. When he falls, it's a long way down. It's the fall you don't walk away from.

The movie focuses, of course, on brilliant Joe. He's haunted by his decision and by the corpse of the stranger who gave so much more than he did, even if futilely: The balloon set down a few hours later and the boy was fine. Joe's friends think he's a hero -- he did act with risk to his own life -- and it's easy for him to play the man of action, but the actor is brilliant in letting us see the insidious little worms inside Joe's head. He feels he wasn't really heroic. He secretly suspects he was the first to let go. He may have betrayed the others. He may even have killed the man -- a doctor, of course, a good and decent man -- who ultimately fell.

So Joe's life is in quiet turmoil, his doubts infecting his love life (Samantha Morton plays the lover) and his professional life, but he seems to grimly soldier on. He'll get over it . . .

But then there's Jed. Jed was one of the other men who let go, and he seeks out Joe. Rhys Ifans (remember Hugh Grant's roommate from "Notting Hill"?) plays Jed. He's squirrelly, odd, generating a faint vibration of dysfunction. The audience knows before the brilliant Joe: Jed's bad trouble.

At first, he just wants to talk and the dutiful Joe, who feels infinitely superior, condescends to permit this imposition. But Jed, it turns out, wants more; he thinks the dreadful event somehow consecrated a love between he and Joe and he wants into Joe's life, into his head and, one assumes, into his body. The homosexual insinuation is one thing; but it seems there's more, really, that Jed wants and that's the truly disturbing part. He wants into Joe's privacy, he wants into his intimacy, he wants all boundaries between them to be down. Now that's icky!

So the movie turns out to be an excruciating ordeal by stalker, as Jed dogs Joe, ever more insistently, ever more crazily. Somehow, Joe figures that the one way to be quit of this is to confront the situation frontally and figure out, once and for all, what happened that day, what drew these people together and whose responsibility it was.

Michell and Craig directed and starred in, respectively, last year's "The Mother," which reached Washington just a few months ago. Michell is a clear, incisive craftsman of the old school, who works cleanly and honestly. There are no film school tricks, just a shrewd grasp of milieu (intellectual London) and narrative (straight ahead). He and Craig connect brilliantly, and the film, which builds to an act of violence as much as an act of understanding, is one of those experiences, like the creepy Robin Williams classic "One Hour Photo," that lingers in the mind.

Enduring Love (91 minutes, at area theaters) is rated R for violence, language and sexual innuendo.

Daniel Craig and Samantha Morton are lovers in Roger Michell's taut, twisted thriller.