Set in October 2003 on the campus of Harvard University, The Social Network opens with protagonist Mark Zuckerberg arguing with his girlfriend, Erica Albright, over beers. Erica accuses Mark, a Harvard sophomore, of being obsessed with the idea of which all-male final club (akin to a fraternity) he could get into. Mark tells her that he is ambitious, not obsessed, and says she should be more supportive because his acceptance into the club will mean she, a Boston University student, will meet people she wouldn't otherwise. Insulted, Erica tells him she is breaking up with him.
Mark returns to his dorm room and posts to his blog that Erica is a bitch with small breasts. He then hacks into the "face books," or online photo directories, of various on-campus organizations to collect photos of women. He writes code for a website called Facemash and posts the photos. Users are invited to rank which of two photographs is the "hotter" woman. His friend Eduardo gives him a chess player–ranking algorithm to score the women. After the site gets significant traffic, the administration shuts the site down. Mark goes to a disciplinary hearing and is unrepentant. He tells them he deserves recognition for pointing out flaws in their computer security.
Cameron and Tyler Winklevoss and Divya Narendra read about Facemash in the Harvard Crimson newspaper. They invite Mark to build their dating website, TheHarvardConnection.com. Mark agrees, then goes to Eduardo with an idea for an exclusive social networking website.
At a deposition hearing in the future, a lawyer asks Mark about when he went to Eduardo. Eduardo explains that they split the company 70/30, and that Eduardo was made CFO of The Facebook. At another deposition, the Winklevoss twins and Divya are also suing Mark: they claim he stalled work on their website while simultaneously stealing the idea and creating Facebook. Mark is sulky and distracted in both depositions.
Back in 2004, The Facebook grows in popularity on campus. Eduardo meets Christy Ling, a woman who seems to be attracted to him because of his involvement in the website. Eduardo sees a cease and desist letter from the Winklevoss twins. Mark says they had an idea, but he had a better one. Eduardo is exasperated with Mark, who insists that he didn't steal their idea or code.
Mark and Eduardo expand the website to include other Ivy League schools. Sean Parker, founder of Napster, learns of the website when looking at the laptop of a Stanford student he has just slept with. While the Winklevoss twins go to the president of Harvard with their complaint against Mark, Mark and Eduardo seek investors and advertisers. They also meet with Sean, who wows Mark with his confidence. Sean tells them they have a billion-dollar idea and insists Mark move the company to Palo Alto to be close to Silicon Valley's tech giants.
In the summer, Mark rents a house in Palo Alto using $18,000 Eduardo provided for business expenses. Eduardo stays in New York to take an internship in business. Sean happens to be staying across the street from Mark. Sean disapproves of Eduardo looking for advertisers in New York and insists Mark was right to move. Mark is impressed that Sean is dating a Victoria's Secret model. He asks Sean to move in to the house, knowing he has nowhere to stay.
Eduardo arrives from New York soaking wet because Mark forgot to pick him up from the airport. He is upset to learn Sean is staying at the house rent-free and that he has been made president of the company, setting up meetings with investors. Eduardo returns to the east coast and freezes Facebook's bank account to punish Mark for leaving him out of decisions. Mark calls to get angry at Eduardo, but then he also shares the news that Peter Thiel, one of the PayPal founders, has invested half a million dollars in Facebook.
Eduardo flies to California to sign documents concerning his 34% share in the newly incorporated Facebook. He doesn't realize that he is agreeing to have his share diluted considerably. When he learns of his reduced ownership, he breaks Mark's laptop. Mark tells him he made a poor business decision while Eduardo insists Mark set him up. Security walks Eduardo out of the offices. Facebook then reaches one million users.
At a sorority party, Sean is caught by police doing cocaine with underage Facebook interns. He phones Mark from the police station and Mark is angry that Facebook's image will be tarnished in the newspapers. In the future, Mark sits alone at his laptop in the deposition boardroom after everyone else has left. His lawyer comes in and tells him he will just have to settle with the Winklevoss twins and Eduardo because it'll be easier than going before a jury.
She leaves the room and Mark goes to Erica Albright's Facebook page. He sends her a friend request and then continuously refreshes the page, waiting for her response. Text over the screen informs the audience that the Winklevoss twins were given a $65 million-dollar settlement, Eduardo settled for an undisclosed amount, Facebook has half a billion users, and Mark is the youngest billionaire in the world.
