The CSIs get a lead on the assassin who escaped them in "Down the Rabbit Hole", but when they descend up on the warehouse where she's been hiding out, they find her dead body, a knife sticking out of her head. In the morgue, Sid extracts the knife and hands it to Mac, who recognizes it as a Navy Seal weapon. Sid also points out that the victim, Suspect X, has had extensive plastic and reconstructive surgery. Mac asks the coroner to try to deconstruct the victim's face in the hopes of IDing her. Adam finds a piece of shrapnel in the hilt of the knife, and Mac suspects that the Navy SEAL it belonged to may have been wounded in battle, meaning he would have received a Purple Heart medal. When Danny and Lindsay connect the knife to the New Jersey judge Suspect X murdered, Mac thinks the man's son, a wounded vet named Russ McHenry, could be the killer. Mac and Flack question the young man, but they see three of his limbs have been replaced, and though he insists he'd be capable of killing someone, he tells them he didn't know the killer's identity. Danny finishes the facial reconstruction on the computer and makes a startling discovery: the dead woman wasn't Suspect X. Danny found the woman's real likeness in the missing person's database: her name was Katie Mann. Suspect X attempted to use Katie to fake her own death.
The CSIs learn Katie was the assistant to the mayor's criminal justice coordinator, Jordan Gates. Mac and Jordan are friends: he helped her out when her ex-husband was stalking her and in turn she aided him in getting his lab reconstructed after a bomb he set to catch a killer blew up. Jordan is shocked to learn that Katie is dead. She tells Mac and Flack that she reported the girl missing two months ago, and recalls that Katie was going to go to Club Random the night she disappeared. Danny and Flack go to Club Random, the cosplay club where many Second Lifers hang out. When the Second Life interface on the screen at the club is hijacked, the two realize that Suspect X is watching them. Lindsay comes up with another lead: she traces the plastic surgery materials to a Dr. Joseph Kirkbaum, who lost his license after a woman named Lori Hess sued him. Lori was killed execution two months ago, and Mac surmises Suspect X killed her in exchange for the plastic surgeon operating on Katie. Angell, Flack, Danny and Lindsay go Parkbaum's office. Danny and Lindsay discover Kirkbaum held Katie in his embalming room, and they make another gruesome discovery: Kirkbaum himself has been murdered and left for them to find, a camera in his eye. Danny dislodges it and breaks the cord, realizing they were once again being watched by Suspect X.
Adam makes a major break in the case when he goes over Kirkbaum's subpoenaed electronic records and discovers Suspect X contacted him after he sent several heated e-mails to his attorney. Adam surmises Suspect X was using a spider search to find keywords and phrases in people's e-mails identifying them as potential clients. Mac has Adam set up several e-mail addresses hoping to lure the assassin to them. Hawkes identifies a bottle of liquid the killer left behind in a jumpsuit as feral liquid, indicating she was working with sound systems at some point. Mac recalls the big rally Jordan Gates is planning features a large sound system. Mac, Danny and Flack rush to the event and Danny discovers a gun concealed in a speaker. They managed to thwart the assassin this time, but Mac warns Jordan that the mayor or some other official is in danger. Adam has good news for Mac: he's gotten a hit on one of the e-mail addresses. Mac sets up an undercover operation with Angell posing as the woman Suspect X thinks will hire her. Suspect X shows up, but a random cop spooks her and she runs, with Mac hot on her trail. He chases her to a building under construction and the two exchange gunfire. Mac fires a fatal shot, and as she's dying, he asks her what was in it for her. She tells him of the thrill of killing a person as she dies, dropping her gun to the ground. Mac has some frightening news for Jordan: her ex-husband had hired Suspect X to kill her.