Primetime

In 2006, journalist Chris Hansen hosts the show To Catch a Predator on NBC, conducting sting operations with the help of an anti-pedophile vigilante group called Perverted-Justice, led by Xavier Von Erck. Luring would-be predators to a house where they expect to engage in sex with a minor (played in person by a decoy actor of legal age), they are confronted by Hansen and his camera crew before being arrested by police. Hansen and his producer, Andie Bender, meet with NBC head Jeff Zucker, who acknowledges the show's ratings success despite his personal distaste for its content and puts it in the primetime slot, competing with ABC's hit show Lost.

Aspiring actor Dan Plum, looking to gain credits for membership to the Screen Actors Guild (SAG), is cast as one of To Catch a Predator's decoys, requiring him to pretend to be a teenage boy. Although he is initially disoriented and disturbed by the shooting process, he acclimates to the job and comes to admire Hansen. Meanwhile, in Fort Myers, Florida, Hansen breaks off an affair with a younger woman at a restaurant, unaware that he is being photographed. A reporter for the National Enquirer later makes threatening calls asking for comment on an upcoming story about Hansen's extramarital affair.

Hansen becomes consumed by his desire to make To Catch a Predator the biggest show on television. He is disturbed by further calls from the National Enquirer, as well as an accusatory encounter with a rabbi caught in a sting. An executive from ABC attempts to poach Andie to produce a show inspired by the success of To Catch a Predator called What Would You Do?; Andie initially declines, but reconsiders as Hansen's behavior grows increasingly erratic. Dan worries that To Catch a Predator will not advance his career the way he hoped. Hansen tells him that their work is "cleansing the world of an ancient evil", giving him a bracelet he received in India while investigating a story about the mysterious disappearance of children.

After a letter from a police officer in Murphy, Texas prompts Xavier to search for pedophiles in the area, he finds one prospective predator who covers his tracks more diligently than most, before revealing that he is attending a wake in nearby Denton. Finding that the only funeral in Denton at that time is for a Texas state senator, Xavier surmises that the predator may be a member of the government. Under pressure from the network to improve ratings and eager to catch a high-profile "whale", Hansen cancels an upcoming shoot in New Jersey over Andie's objections and takes the To Catch a Predator team to Texas.

The "whale" is reluctant to meet in person, but eventually gives his phone number to Xavier, revealing that he is assistant district attorney Bill Conradt. While Andie is reinvigorated by this success, calling ABC to tell them she will not join What Would You Do?, Dan becomes disillusioned with his work when speaking to Conradt over the phone. Forgoing the usual protocol, Hansen decides to bring the sting operation to Conradt's house, which is surrounded by heavily armed police officers. Hansen receives a call from his wife, Mary, who tells him the reporter for the National Enquirer called her for comment about Hansen's affair.

As Hansen and the police prepare to move in, Conradt glares at Hansen through a window before shooting himself. Disappointed that they did not get to interview Conradt, Andie matter-of-factly plans to interview the police officers in order to salvage the episode, while a crying Hansen stares numbly into the distance, repeating his various catchphrases. A badly shaken Dan walks away from the scene; a year later, living in Mesa, Arizona, he receives his SAG card in the mail.