SOME 300 YEARS after Pierre Choderlos de Laclos published his shocking account of erotic gamesmanship, "Les Liaisons Dangereuses," France is no doubt a more humane place. You'd never guess that, however, from "Love Me if You Dare," writer-director Yann Samuell's sugarcoated yet blackhearted tale of an obsessive relationship. It's a nasty piece of work about two nasty pieces of work.

The story's fateful connection is made when Sophie (Josephine Lebas-Joly) and sometime narrator Julien (Thibault Verhaeghe) are both 8. The boy's golden-lighted childhood has just been darkened by the diagnosis that his mother has terminal cancer. Feeling aggrieved, Julien bonds with Sophie, who's regularly tormented for being Polish and poor. Julien gives his new friend his most precious possession: a tin box, decorated with the image of a carousel, that he received from his mother. Soon, the box is passing regularly between them; the current owner is whichever of the children who has most recently fulfilled a dare issued by the other.

As 8-year-olds, the kids torment their elders with rude words and show each other their private parts. By the time they get to college a decade later, Julien (now Guillaume Canet) and Sophie (Marion Cotillard) are best friends who still share a bed and pre-breakfast pillow fights. Their bratty games have become more brazenly sexual: Julien dares Sophie to go to an oral exam wearing her underwear outside her clothes, and she in return challenges him to seduce a classmate and bring the woman's earrings to her for proof.

Worried that his son is wasting his college years, Julien's father tells Sophie to get lost and his son to get serious. Accepting this advice, Julien informs Sophie he has to study harder. Insulted, she responds that she'll see him in a year. Four years later, budding businessman Julien locates Sophie in the cafe where she's a waitress. A romance seems to begin, but it turns out that Julien is just setting up Sophie for the cruelest gag yet: pretending to ask her to marry him when he actually intends to wed someone else. ("Love Me if You Dare" is definitely not designed for the audience that eats up "The Bachelor" and other happily-ever-after fare.) Sophie is not amused by Julien's mock (and mocking) proposal, yet the relationship doesn't end. Even as they settle down with other people, Sophie tells Julien they'll meet again in 10 years. In a sense, the film maintains, they'll be together forever. Samuell concludes his tale with two possible scenarios for the couple's eternal connection. One is sentimental and the other sensationalistic -- which just happen to be the two poles of the movie's sensibility.

Although not quite as nostalgic as "Amelie," "Love Me if You Dare" aspires to a similar sort of vision of France as a fairy-tale universe: never-never land, but with sex. Samuell supplements his dreamlike camera effects with animation and scores the story to what may be every version ever recorded of that Gallic chestnut, "La Vie en Rose" -- from Edith Piaf to Louis Armstrong to Donna Summer. (Alas, Paris synth-punk outfit Metal Urbain never took a crack at the tune.) As the game gets meaner and more destructive, the film's ambience remains resolutely cute.

It's hard to empathize with either Julien or Sophie, but Samuell's attitude toward the latter is revealing. The two characters attend the same college, yet after graduation Julien becomes a white-collar executive while Sophie is first a waitress and then a gold digger, marrying a wealthy, slow-witted soccer star. At least Amelie was allowed to exercise some control over the cartoon Paris she inhabited. Even though she's the more audacious of the two players, Sophie is essentially trapped in someone else's game. "Love Me if You Dare's" universe may be fantastical, but it's still a man's world.

LOVE ME IF YOU DARE (R, 94 minutes) -- Includes sexual situations, profane language, comical depictions of urination and risky business. In French with subtitles. At Cineplex Odeon Shirlington and Landmark's E Street Cinema and Bethesda Row.

Guillaume Canet and Marion Cotillard in "Love Me if You Dare."