Burn After Reading

Osbourne Cox (John Malkovich) is a CIA analyst who quits his job at the agency after being demoted, ostensibly because of a drinking problem. He then decides to write a memoir about his life in the CIA. His wife, pediatrician Katie Cox (Tilda Swinton), wants to divorce Osbourne and, at the counsel of her divorce lawyer, she copies many of his personal and financial files off his computer and onto an optical disc. The lawyer's receptionist accidentally leaves the disc at Hardbodies, a workout gym. After her husband is served with divorce papers, Katie changes the locks to keep him out of their house.
An employee of the gym, Chad Feldheimer (Brad Pitt), obtains the disc from the gym's custodian. Seeing the content of the memoir, he assumes that it is highly classified information and the financial data is some sort of cipher. Along with his fellow employee Linda Litzke (Frances McDormand), he intends to use the disk to blackmail Osbourne; Linda wants the money to pay for cosmetic surgery. Chad meets Osbourne, who refuses to pay and punches Chad in the nose. Then Linda decides to take the information to the Russian embassy. At the embassy, she hands the disk over to the Russians, promising that she will give more information afterwards. Because Linda and Chad don't have any more information, they decide to break into Cox's house.
Katie has been having an affair with Harry Pfarrer (George Clooney), a womanizing Treasury agent. By chance he has recently met Linda online and begun an affair with her as well. Chad stakes out the Coxes' house and breaks in when he sees Harry and Katie leave. Harry, however, comes back, finds Chad, and accidentally shoots him in the face. Linda had told Chad to carry no ID and cut the labels out of his clothes; when Harry sees this, he thinks Chad was a spy and disposes of the body.
Days later, paranoid since he killed Chad, Harry leaves the Cox residence after a fight with Katie. On his way to leave, he manages to tackle a man who has been trailing him for some time, thinking he was working for the CIA or some other government agency. Harry now finds out that the man is working for a divorce firm hired by his wife who, it is later revealed, has been cheating on him as well. Harry is devastated and goes to see an agitated Linda, who confides in Harry that her friend Chad is missing; he agrees to try to help.
The next morning, Harry and Linda meet in a park and she provides him with more information about Chad's disappearance. When he realizes that Chad is the man he killed, he becomes more paranoid and flees in terror, assuming that Linda is also a spy. Linda then turns to Ted Treffon (Richard Jenkins), the manager of Hardbodies, who has feelings for her. Believing that the Russians have kidnapped Chad, he agrees to look for more information in Osbourne's computer. But Osbourne, finding that Katie has emptied their bank account, decides to break into his own house with a hatchet to take her jewelry. Finding Ted at his computer, Osbourne shoots him. Ted survives and runs out of the house, but Osbourne grabs the hatchet and kills him in broad daylight. 
The movie ends by returning to the CIA's headquarters, where an official (David Rasche) and his director (J.K. Simmons) are trying to sort out what happened: Chad is dead, Ted is dead, Osbourne is in a vegetative state after being shot by an agent while attacking Ted, and Harry and Linda have been arrested. Harry was trying to board a flight to Venezuela, and the director decides to let him go so he's out of their hair. Linda promises to remain silent if the CIA will finance her plastic surgery. The baffled CIA agents agree to her terms, but decide that they have learned their lesson: they will never repeat whatever it is that they did in this case; though they are still not clear what it is they did or what they learned, if anything.