Petty thief Louis "Lou" Bloom is caught stealing from a Los Angeles railyard by a security guard. He attacks the guard, steals his watch and leaves with stolen manhole covers, fencing, and other materials. While trying to sell the materials at a scrap yard, Lou asks for a job, but the foreman, who has already been questioned by police looking for the manhole covers, refuses to hire a thief. While driving home in his beat-up Toyota Tercel, Lou sees a car crash and pulls over. Stringers—freelance photojournalists—arrive and record two police officers pulling a woman from the burning wreckage. One of the stringers, Joe Loder, explains to Lou that they sell their footage to local news stations.
Inspired, Lou steals an expensive bicycle and pawns it for a camcorder and a police radio scanner. After two unsuccessful attempts at recording incidents, Lou records the aftermath of a fatal carjacking and sells the footage to KWLA 6. The morning news director, Nina Romina, tells him the station is especially interested in footage of "graphic" accidents and violent crime in affluent, predominantly white areas. Lou hires an assistant, Rick, a young homeless man desperate for money. To give his footage more impact, Lou tampers with crime scenes, in one case moving a body to get a better camera angle. As Lou's work gains traction, he buys better equipment and a faster car (a red Dodge Challenger).
Lou pressures Nina into a date, telling her he knows she is desperate for higher ratings. On their date, he threatens to terminate his business with Nina unless she has sex with him, and it is implied that she acquiesces. Lou turns down an offer to work for Joe, but when Joe beats him to an important plane crash story, Nina demands that Lou get better footage and keep his end of their bargain. In retaliation, Lou sabotages Joe's Ford Econoline van; when it crashes, Joe is severely injured and Lou records the aftermath.
Later, Lou and Rick arrive before the police at the site of a triple-homicide home invasion in Granada Hills. Lou records footage of the gunmen leaving in their Cadillac Escalade and of the victims in the house, and later presents footage to the station with the perpetrators edited out. The news staff frets over the ethics of the footage but Nina is eager to break the story. In exchange, Lou demands public credit and more money. Police detective Frontieri shows up at Lou's apartment to question him about his connection to the home invasion. He gives her edited footage of the incident, cutting out the parts with the gunmen.
That night, Lou and Rick track down the driver to his house, staking out the house until he leaves to pick up his partner. Lou wants to follow them to a more crowded public area, then call the police and record the ensuing confrontation. Alarmed, Rick demands half of the reward money for locating the gunmen, threatening to tell the police about Lou's withholding of evidence. After some back-and-forth, Lou agrees.
When the gunmen stop at a restaurant, Lou phones the police, warning them that the suspects are armed. They arrive and exchange gunfire. A police officer is shot and one of the killers is gunned down while the other manages to escape in the Escalade. The police give chase. Lou and Rick follow close behind in the Challenger, filming the chase as it happens, culminating in a long multiple-car collision. After the gunman's Escalade crashes, Lou approaches the vehicle, claiming that the gunman is dead and urging Rick to film him. The gunman is revealed to be alive as he shoots Rick, flees, and is killed by arriving police officers. As Rick lies dying, Lou films him and tells him that he cannot work with someone who successfully extorted him for withholding evidence, because he knows it will happen again.
Nina is awed by the chase footage and expresses her devotion to Lou. The news team discovers that the home invasion was actually the criminals breaking in to steal cocaine that the homeowners were stashing; Nina refuses to report this information to maximize the story's impact. Police try to confiscate Lou's footage as evidence but Nina defends her right to withhold it and airs it immediately. Lou voluntarily speaks with Detective Frontieri. While being interrogated by Frontieri, Lou fabricates a story about the men in the Escalade following him; Frontieri knows he is lying, but cannot prove it. Later, Lou hires a team of interns to expand his business, saying that he will not ask them to do anything he is unwilling to do himself.
