Beyond the obvious (money, sex, fame) it’s hard to know what truly pushes Mark, whose personality emerges in furtive smiles, gushes of words and painful pauses. Eventually everyone does pay: the Winklevosses, Eduardo, even Mark. The filmmakers have their ideas about who did what to whom, but they don’t try to fill in all the blanks or, worse, soften Mark’s edges with a Psych 101 back story. You see what turns him on: software, revenge and, in several lightly comic and darkly foreboding scenes, Sean Parker, the flamboyant co-creator of Napster, who’s played by Justin Timberlake as a jittery seducer. Sean oozes into Mark’s life for a piece of the action and instantly dazzles the younger man with his bad-boy ways (coke and Champagne for everyone!), sexy dates and big, brash talk of riches.

Shooting in digital and working with the cinematographer Jeff Cronenweth, Mr. Fincher turns down the lights and tamps down his visual style, deploying fewer special-effects sleights of hand than he did in “The Curious Case of Benjamin Button,” with its wizened and baby Brad Pitt, while also maintaining the familiar Fincher atmosphere of dread. Harvard has rarely been represented to such dolorous effect as in “The Social Network,” where even the colors seem leached of joy. A restrained, somber palette and the shallow depth of field express the limits of Mark’s world, while the rapid, seamless cutting among different times and spaces — scenes of him creating Facebook are woven together with scenes of him in separate depositions — evokes the speed of his success, giving the narrative terrific momentum.

Mr. Fincher pointedly abandons his smudged browns for a gauzily lighted sequence of the twins rowing at a tony British club that, with the edges of the image blurred and movements slowed, looks like a dream. This is a world of rarefied privilege in which men still wear straw boaters, and royalty blathers within earshot. Mark isn’t invited, not because he’s poor (he isn’t), but because this is a closed, self-reproducing system built on exclusivity and other entitlements, including privacy. (The movie refers to Mark’s being Jewish, and the twins look as if they crewed for the Hitler Youth, but that’s just part of the mix.) Mark doesn’t breach this citadel, he sidesteps it entirely by becoming one of the new information elite for whom data is power and who, depending on your view of the Internet, rallies the online mob behind him.

“The Social Network” takes place in the recognizable here and now, though there are moments when it has the flavor of science fiction (it would make a nice double bill with “The Matrix”) even as it evokes 19th-century narratives of ambition. (“To be young, to have a thirst for society, to be hungry for a woman,” Balzac writes in “Le Père Goriot.”) The movie opens with a couple in a crowded college bar and ends with a man alone in a room repeatedly hitting refresh on his laptop. In between, Mr. Fincher and Mr. Sorkin offer up a creation story for the digital age and something of a morality tale, one driven by desire, marked by triumph, tainted by betrayal and inspired by the new gospel: the geek shall inherit the earth.

“The Social Network” is rated PG-13 (Parents strongly cautioned). The usual college high jinks, drugs, drinking and semi-naked women.

THE SOCIAL NETWORK

The film, to be shown on Friday on the opening night of the 48th New York Film Festival at Lincoln Center, opens nationally next Friday.