At the station, Hale and Carter are worried about Cavanaugh's safety. At home, Cavanaugh, aware that something is wrong, opens his front door. A gunshot goes off. Cut to 36 hours earlier. Cavanaugh is stressed out. Hale and Carter meet up with him at a scene, where a young woman has been murdered. The catch is, the killer has documented his own crime scene. Bullet traces, marked evidence, everything. A completely professional job.
Hale and Carter struggle with the lack of evidence on the scene. Carter notices a spot of paint on a footprint and orders a test. The paint tests positive for a chemical used on boats. Hale and Carter head to the marina. In a nearby locker, the cops find a t-shirt and a pair of shoes that match the footprints. Testing DNA from the t-shirt, the lab finds a match -- Rich Kallick, who was arrested by Cavanaugh in the past for another murder. Problem is, he died in custody two months ago. And his body's been cremated. So who would want to frame a dead man?
Looking through the murder book, Hale and Carter head to a motorcycle shop, the scene of a similar murder. Hale quickly finds a bullet that wasn't originally discovered. It's a .22. Kallick was holding a .25 caliber handgun when he was arrested. Then Cavanaugh gets a call from the real killer, who tells Cavanaugh to go public and admit he arrested the wrong man. And have a cigarette if it'll help calm him down. Cavanaugh realizes that the killer has been inside police HQ.
Scanning security footage, Hale and Carter find a suspect. Hale begins to realize that the pattern of the murders match an ultra-violent video game that people play online. Interrogating the game's maker, the police learn that a group of players were kicked offline for hacking the game. And this was right around the time the first murder occurred. The developer provides Hale and Cavanaugh with the names of the 70 people that were blacklisted.
Cavanaugh gets another call from the killer, who's sitting in a game room that's a combination of Swordfish and Sliver. Hale, playing the game, thinks he knows where the killer will strike next -- a college campus. In a dorm room somewhere, Cavanaugh's daughter wakes up and discovers that her room has been turned into a crime scene. Enraged, Cavanaugh calls out the killer on the local news, calling him a coward.
The police match up one of the remaining gamer names and race to a location. At the same time, the killer leaves, setting a device before he goes. As the police storm in, the computer equipment explodes. Back at home, Cavanaugh is having his family pack up to head out of town for a while. And the killer is lurking around the house. Cavanaugh opens the door and there's a gunshot. It's Hale, icily icing the gamer killer.