The movie starts with a young homeless man running through the street. He runs through several stores, jumping down staircases while continuously looking over his shoulder. He eventually hides under a tunnel behind some boxes and garbage cans. As he looks out from behind the cans, he is shot in the head and the spine by a man (Michael Berresse) carrying a silver briefcase. As he begins to walk away, a pizza deliveryman cycles by and sees the dead homeless man and the gun in the assassins hand. As he tries to get away, the assassin shoots him twice. As hes about to finish the job, a group of people come out of a nearby restaurant. The assassin turns and runs away before the bodies are noticed.
The next morning, Cal McAffrey (Russell Crowe), a writer for the Washington Globe, is driving to the scene of the crime. He bribes the detective, Donald Bell, (Harry Lennix) with coffee and convinces Bell to share some information with him anonymously. The police believe the incident was drug related and that the pizza delivery guy was just collateral damage. Bell also tells Cal that the deliveryman is in a coma, but not dead. As Cal and Bell talk, a girl is seen watching them from above the tunnel.
The next scene shows Sonia Baker (Maria Thayer), an aide to Congressman Stephen Collins (Ben Affleck), getting ready to go to work. She leaves her house and goes to the train station. As she is waiting in a crowd to get on the train, she falls onto the tracks and is killed. As Congressman Collins arrives late for work, he is told of Sonia's death right before his Committee Hearing with military contractor Point Corp. He begins the hearing by announcing Sonia's death (she was lead researcher on Collins investigation) and starts to breakdown in front of the cameras. This causes a media firestorm since Collins is married and leads to speculation that he was having an affair with Baker.
Cal is working on the shooting when Della Frye (Rachel McAdams), pays him a visit requesting dirt on Collins for her Washington Globe blog since she heard that Cal and Collins were roommates in college and fairly close. After Cal insults her work and professionalism, Frye walks away. Cal is called into the chief editors office on Dellas behalf. The Editor, Cameron Lynne (Helen Mirren), asks Cal to provide Della with information on Collins, which Cal flat out refuses.
That night, Cal is writing an article on the shooting when Collins turns up at his apartment. The two talk for a bit and Collins tells Cal that his wife isnt talking to him, reporters are camped outside his house and that he has nowhere else to go. Cal tells Collins that in order to preserve his image he will need to immediately call Sonia's family and offer his condolences since the press at large believes that Sonia killed herself when Collins refused to leave his wife. Collins then shows Cal a video sent to him from Sonia that morning in which she made tentative plans for that weekend. Cal, realizing the significance of the video, tells Collins that the video alone can prove that it was not a suicide and save Collins career. He tells Collins that he should use Sonia's accidental death to exploit the lack of safety of the public transport system. Collins, however, suggests that Sonia may have been murdered.
Cal calls Della at 3 AM and tells her to meet with one of his police contacts in order to see the footage from the train station. Reluctantly, Della agrees to meet the contact and see the footage. She finds nothing because Sonia was in a blind spot and there was no recording of her on the platform before she fell.
Cal continues following up the shooting. He goes to the morgue to see the body of the homeless man. The coroner lets him in and while they talk, Cal copies all the numbers from the mans cell phone. Just before he leaves he buys a soda from a vending machine and as he turns around, he sees the girl from the tunnel. She makes him buy her a soda too, which he does, and he leaves. Once in his car driving down the road, he begins dialing all the numbers. After reaching a drug dealer, a disabled number and a voicemail, Cal ends up reaching the voicemail of Sonia Baker!
Cal interrupts Della's meeting in order to see if Della found a link between Sonia and drugs. Della is upset that Cal would seek to ruin whats left of Bakers reputation. Cal becomes suspicious of a deeper connection. He goes out to get lunch when his bag is stolen. He runs outside to look for it and sees across the street the homeless girl from the tunnel holding it. She offers to tell him what was in the last bag the dead man had stolen before he was killed.
She takes Cal to an underground sewer maintenance and shows him the contents from the metal case the homeless man stole. She explains that they would steal businessmens bags and sell them back for a price. The girl tells him that the case had a gun with weird bullets and a bunch of photographs of Sonia. She used the mans phone to call Sonia but she didnt pick up. Despite the girls objections, the homeless man agreed to meet with the assassin to sell back the bag. But he killed him and took the case, without knowing the photos were missing.
Cal gives her 500 dollars and takes the photos back to his editor. He, Della and Cameron talk to the legal advisor of the paper who tells them that they can hold onto the photos for 48 hours max before the police can take them away from the paper. Cameron wants to have Cal work on the case with a more experienced political reporter, but Cal is firm in having Della help him out. Cameron is angry that Cal isnt giving her a scoop on Congressman Collins and tosses him a newspaper with an article on Collins character, which shows him with his military friends from his army days. Cal tells Della to go and visit the pizza deliveryman in the hospital since he seems to be coming to and may have information. While Della goes to visit the deliveryman, Cal goes and has a drink with Collins' wife, Ann (Robin Wright Penn).
Della arrives at the hospital and passes a man in the hall (the assassin). She makes her way into the deliveryman's room but is shouted at she is not allowed to be there by nurses. When the cop watching starts to take her out of the room, bullets are fired into the room from the opposite building. The deliveryman is killed and the cop is injured. Della is left staring at a pool of blood in shock. This confirms Cals offhanded theory that a professional was hired to take care of Sophie Baker.
Cal gets Dellas call and rushes to the hospital. He comforts her and makes sure shes all right before taking her back to the paper. At the paper, Cameron (Cam) and the others call Detective Bell and hand over the photos. Bell and his attorneys are angry that Cal didnt immediately contact them about the photos and tells them that the deliverymans death is on their hands. Cal presents his theory that Point Corp was behind the murder of Sonia Baker, but Bell shakes off the notion as nothing more than a conspiracy theory fit for a television show (joke reference to Lennixs role on '24').
Cal and Della are now convinced that Point Corp was behind the deaths of Sonia Baker, the homeless man, and the deliveryman. Della reviews the security footage from the train station and sees the assassin in the crowd. Cal and Della start digging into Point Corp and Sonia's personal history respectively. They discover that Point Corp had created a series of fronts so that they could buy up domestic security contracts. Cal meets with a Point Corp contact who tells him that the assassin worked for an old military contractor. The contact gives Cal the address and Cal sets out to find some answers.
Cal arrives at the old contractors building and knocks on the door of the apartment. The apartment door is open due to a sock propped in the corner. As he is about to enter, the assassin arrives carrying a laundry basket. Cal recognizes him and begins making small talk in order to distract the assassin. Once the assassin goes into the room, Cal runs and calls the police. He makes his way to the lobby. As he prepares to go outside, he sees a figure of a person walk toward the enclosure and pass behind a pillar. When it doesnt reappear, Cal takes a side door and enters the complexs garage. The assassin begins looking for him in the garage. After successfully avoiding him, a group of people enter the garage and get in their car. Cal realizes that the assassin knows where he is. When the people drive their car toward Cals hiding spot, Cal jumps onto the car and narrowly avoids being shot. The assassin is about to shoot at Cal again, when Cal throws himself behind another car. The police arrive and the assassin escapes out of a side door.
Detective Bell is furious that Cal went after the assassin. Cal assures him that it was purely a coincidence and that he had been chasing a lead. Bell is skeptical. Bell tells Cal that the homeless girl who gave him the photos turned up dead that morning.
Della tells Cal that she tracked down Sonia Bakers old roommate who tells her that Sonia and the roommate had a threesome with Congressman Collins and that Sonia had a very large debt, which Collins paid. Cal disregards this theory as bull and goes back to the photos. Cal tells Della to identify a man in one of the photos of Sonia before calling it a night. When he arrives home, he sees Ann Collins sitting on his doorstep. They talk for a bit. It is revealed that Cal & Ann had been lovers but Ann married Collins because Cal wouldnt step up. Cal asks if Collins could have acquired a large amount of money without Ann knowing. She becomes upset after realizing that she is nothing more than a source and walks away. Before she walks out, she tells him that Collins could not get that much money without her knowing since they had two mortgages and spend everything they make paying it off.
Della tells Cal that the man who was in the photo is Dominic Foye (Jason Bateman), a PR rep for Point Corp. Cal meets with Collins to ask him about Sonia's history and about what he and Sonia found out about Point Corp. Collins reveals that their investigation into Point Corp indicated that Point Corp was using dummy corporations to bypass monopoly laws and buy up all the available domestic defense contracts offered by the government. He makes it explicitly clear that if Cal can prove the tie between Point Corp and Media Corp (the largest of the dummy corporations), Collins will go on the record about the ties and blow the conspiracy wide open.
Cal and Della arrange to have Foye talk about his connection to Point Corp on record and tell them everything about Sonia Baker. After successfully scaring Foye into thinking he is surrounded by Point Corp associates, Cal takes him to an out of town motel. There he negotiates with Foye and convinces him to go on record. He tells Cal that Point Corp needed a girl for one of their business deals and Sonia was the first person that came to his mind. She was in debt, so Point Corp agreed to pay her 26,000 dollars a month to spy on Congressman Collins. Cal calls Collins and asks him who recommended Sonia. He then tells Collins to meet him at the motel.
When Collins shows up, he tells Cal that Congressman Fergus (Jeff Daniels) recommended Sonia to him because Sonia was the daughter of an old family friend. Cal shows Collins the recording of Foye and specifically shows him the part about Point Corp. However, Cal lets the tape run further than intended and Collins finds out that Sonia was pregnant with his baby when she died and that she had stopped spying on Collins after she fell in love with him. This revelation sends Collins over the edge and he goes into the next room and proceeds to beat Foye half to death. Cal separates the two and Collins proceeds to mock Cal and leaves.
Cal goes to meet with Fergus and he doesn't confirm anything but when Cal asks for Sonia's mothers name, Fergus doesn't answer. As Fergus walks away, Cal tells him that he's running the story with a link between Fergus and Point Corp as a means of undermining Congressman Collins' investigation. He then tells Fergus that Sonia's mothers name is Janine.
Cal goes and writes a tentative article but Cameron refuse to print it because of the lack of credible sources. As Cam and Cal argue over whether or not they should go to print, Collins walks in with his wife. He goes on the record and tells them everything he found out during his investigation, his relationship with Sonia and his theory that Point Corp is responsible for everything. When hes done, Ann and Cal talk. She tells Cal that she forgave Collins because Sonia was paid to sleep with him for 26,000 dollars a month. Cal and Della start to write their articles. Meanwhile, the assassin is shown dressing up in military gear and arming a rifle.
Cal goes to Della and the two share a drink of whiskey. He presents her with a necklace of pens, however as he begins to talk about his past with Ann, he realizes that she knew a piece of information he hadn't shared with Collins. Collins was never shown the portion of the tape which said Sonia was being paid 26,000 dollars a month. Cal tells Della to hold the front page as he looks at the newspaper Cam tossed to him earlier which showed Collins with his military unit. The assassin is in the photo and his name is revealed to be Robert Bingham.
Cal confronts Collins in his office. Cal asks about Robert Bingham, and Collins tells Cal that Bingham was someone whose life he saved from his army days. Collins hired Bingham to follow Sonia around because, during the affair, he suspected something was off. When he found out she was working for Point Corp, Bingham became upset because he felt that Point Corps mercenaries were a disgrace to the officers of the U.S. military. Collins claimed that he tried to tell Cal the truth, but Cal calls Collins on his lie. He leaves after telling Collins that he already called the police.
Cal walks toward his car and he is confronted by Bingham cocking his gun. He tells Bingham that regardless of the outcome, Congressman Collins has been exposed. Bingham prepares to fire his weapon as Detective Bell and his officers arrive. As Bingham fires, Cal dives out of the way and a hail of bullets take out Bingham.
Cal returns to the Globe, 4 hours after the front page was due. He types up an article exposing Collins and signs it written by Della Frye and Cal McAffrey. He leaves his desk and walks out, letting Della click send for the copy room. She catches up to Cal on his way out and a 'Sent message' appears on the screen of the computer and the movie ends with the credits rollings while the article is printing and being shipped out in the background.