Professor Hayden Parker is at his home recording a podcast denouncing Billy Grimm, the charismatic leader of The Blood. He dismisses Billy as a messianic charlatan, but is interrupted when Kelly comes in with Rebecca Keller, one of Billy's disciples. Kelly explains that Rebecca's husband was one of the men who abducted her sister, and she figures that even though the husband killed himself rather than talk, he told his wife where the sister was hidden. She wants Parker, a deprogrammer, to help her convince Rebecca to reveal what she knows. The lights suddenly go out and Billy's men storm in, tase Kelly unconscious, and leave with Parker and Rebecca.
At Nate's apartment, Jeff logs onto a Cult fansite and reviews Nate's notes about the program. Someone sends him an online message saying that her husband was abducted just like Nate and asks Jeff for help.
The next day, Skye is at the ranch where the compound scenes are filmed. She provides Marti with some info on ballistic trauma so that the actress can get in character while she has Lexi do her makeup. Skye receives a text message from Jeff and Lexi and Marti both wonder if she's stexting with her new boyfriend. They point out that Skye keeps running off to be with Jeff and they figure she's having a relationship. Skye insist that they're just friends with a shared interest.
Jeff goes to Fandomain waits for his contact, Alma, to arrive. Skye shows up first and he explains that he convinced Alma to meet him there a half-hour ago. The research assistant worries that Alma may be one of the True Believers, but Jeff figures that it's worth the risk. Skye notices a man watching them, and he finally comes over and comments on Nate's notebook next to Jeff's laptop. He asks Jeff if he's a Cult fan and Jeff says that he watches the show, but the man figures that Jeff isn't one of "them."
The man, Terrence Ross, gestures Alma over and she explains that Terrence works for her. She and her husband Rami live in Indianapolis and watched Cult from the first episode. Rami was the one who became obsessed with the show, and started receiving strange calls at all hours. One night several people broke in and Rami went to confront them. Alma watched as he left voluntarily with them, and called the police. However, they dismissed her as a crazed fan with an obsessed husband. Alma hired Terrence, a deprogrammer, who finds people that join cults and bring them out.
Alma shows them Rami's notebook the show, which mentions both Los Angeles and True Believers. She and Terrence came to LA and find her husband, and Alma noticed Jeff on the online chat rooms. Skye looks in the notebook and finds a black disk like the one they found in Nate's apartment. Jeff confirms that Alma inserted the disk into her work computer instead of her personal laptop, and suspects that it may not have erased itself because she had no personal data to upload. Alma agrees to let them take the disk but Terrence insists on going with them.
Jeff and Skye leave with Alma and Terrence in tow. The reporter calls E.J. to let her know that he's bringing her an uncorrupted disk. As Terrence and Alma go to their car, Detectives Sakelik and Zavala pull up. While Zavala talks to Terrence, Sakelik warns Jeff that Terrence has been implicated in several abductions and assaults. The police keep running tabs on him and Sakelik explains that Terrence claims to be a self-taught cult deprogrammer. She advises Jeff to stay away from the man while she continues the investigation into Nate's disappearance. Once Sakelik joins her partner, Skye wonders whether they should trust Terrence or Sakelik, and Jeff suggests that they don't trust either one.
The group goes to Nate's apartment and meets with E.J. While she decrypts the disk, Alma looks at Nate's wall of clippings and tells Jeff that Rami had a similar. While he talks about his brother and how it was just the two of them after their parents died, Skye asks Terrence where he learned deprogramming. He says that he just picked it up and warns that Cult may not be an actual cult, but the obsessed viewers act like cultists. E.J. decrypts the disk and locate the IP address where it was burned. She recognizes the address as a hacker hostel where some of her friends have stayed nit he past. Jeff and Skye go to check it out and Terrence insists on going with them.
Billy is busy lecturing a group of Blood children on how to slaughter a pig, and to do it respectfully because it is providing them with food. Once he finishes, he notices his man Gil and the others pull up in a truck. Billy goes to greet them and then opens the bag containing Parker. He cuts Parker loose, wipes his blade on the professor's coat, and suggests that they clean up before dinner.
Sakelik is in her patrol car watching the Parker episode on her iPad when Zavala arrives with coffee. She gets a call and, wanting to take it alone, "accidentally" spills coffee on her. When Zavala goes to get some napkins to clean up the mess, Sakelik calls her people. They tell her that Nate has been moved to a new location and Sakelik brings up Nate's photo on the car's computer.
Billy takes Parker to the middle of a field and sits him down at a table near a tree. As the cult leader enthusiastically cuts off slices of roast pig, he tells Parker that he wanted to meet his unauthorized biographer. He has the manuscript that Parker was writing about him and the professor insists that if he disappears, everyone will know that Billy is responsible. Billy assures Parker that he has never harmed anyone, as the professor well knows, and invites Parker to eat. Parker, his hands nailed to the table, is unable to move.
Jeff, Skye, and Terrence go to the hostel and spot a hacker, Sean, burning the black disks. When they approach him, he runs for it while the other hackers run interference. By the time Jeff and the others get outside, Sean is getting into a car. Terrence shoots him, much to Jeff and Skye's shock, but then reveals that he's using rock-salt loads. The deprogrammer asks Jeff what he's willing to do to save Nate, and loads Sean into a car. Jeff goes to his car to follow, telling Skye that they may not have another chance to find Nate. She insists on going with him and they follow Terrence to his rented apartment.
Alma meets them there and Terrence gives Sean an injection of amobarbital. He assure Skye that he knows what he's doing and explains that the drug should help them get the truth out of the hacker. Terrence asks Jeff for his help and the reporter comes over while a disgusted Skye goes out on the balcony. A few minutes later, Jeff comes out and tells Skye that Sean isn't telling them much. He admits that he has concerns about what they're doing, but insists that they have to find Nate. Terrence comes out and tells them that Sean just keeps muttering "under a tree" over and over. The deprogrammer figures that the True Believers have killed Rami and buried him beneath a tree somewhere. He prepares to drop Sean off in a park to let him sleep off the drug's effects. However, the hacker starts muttering other verses about boxes and Skye recognizes them.
Billy shows Parker the box tattoo that he and the other Blood members wear and talks about the significance of a box in many cultures.
Skye brings up the recording of the episode and show it to Sean. She asks if the tree in the background is the one that he's talking about. Sean mumbles about it being "at the show" and says that no one at the ranch knows. Skye tells the others that she thinks she knows what Sean is talking about.
Billy shows Parker a photo of his son, Michael, and explains that he buried him at the ranch when he died. The cult leader insists that everything that he's done is because of Michael, and stabs the manuscript pages. He demands to know why Parker didn't include Michael in his biography and suggests that Parker omitted the boy because he wanted to demonize Billy. Parker insists that Michael wasn't important to his story, but Billy tells him that family is the only thing that matters. He then takes out photos of Parker's wife, daughter, and grandchild, and talks about how beautiful they are. Billy stabs the photos, pinning them to the table, and orders Parker to never write or say another word about him.
That night, Skye takes Jeff and Terrence to the Guthrie Ranch that they use for the outside shots of Billy's compound on the show. Jeff spots an old drainage pipe and realizes that it leads to an old septic tank like the one he and Nate played in when they went on vacations to a ranch with their parents. They look around for the hatch leading into the septic tank. When Terrence finds it, they realize that there's a new ladder leading down into it.
Sakelik gets Sean released after he's picked up at the park. She has him confirm that Terrence was the one who abducted Sean and that Jeff and Skye were helping. Sakelik forces Sean to tell her that he told his captors about the ranch.
At the ranch, Jeff, Skye, and Terrence climb down into the septic tank and find a series of corridors. They find photos of people taped to the wall, each one with an X through it. The last photo is of Nate, but it doesn't have an X. Jeff hears someone up ahead and runs off to investigate. Skye and Terrence follow and discover that Rami is being held in a room. He has a box of UV glowsticks and angrily tells them to go away and let him solve the puzzle so he can go to the next level. Jeff lights one of the glowsticks and they see that the walls are covered in symbols.
Before they can investigate further, the group hears cars pulling up outside. They climb up with Rami and see men with flashlights approaching them. Jeff wants to stay and examine symbols, but Terrence insists that it's time to go. He drags Rami off to his car and Jeff and Skye have no choice but to follow.
Kelly returns to the compound and Gil and the other cultists briefly stop her. She finds Parker and notices the bandages on his hand, but the professor insists that nothing happened and he didn't get a look at the people who abducted him. When Kelly points out that Billy abducted him, Parker says that the cult leader is innocent and gets into Kelly's car. Billy walks by and nods in greeting to Kelly, who reluctantly drives off with Parker.
The next day, Skye slips away during filming and checks on the hatch. She discovers that someone has filled the tunnel with concrete.
Jeff meets Terrence and Alma at Fandomain as they prepare to leave town with Rami. Alma thanks Jeff for getting her husband back and tells the reporter that Nate is lucky to have someone who will do whatever it takes to get him back. They go outside and, as they prepare to leave, Terrence admits that Jeff did good. However, he tells Jeff that the whole thing got under his skin because he's dealing with a cult that spreads its message through television... and every home has a television.
Later, Jeff meets Skye at Nate's apartment and she tells him about the filled-in tunnel. They figure that the True Believers send the disks to possible recruits, get their personal information, and then abduct them and put them through the initiation. Since Nate's photo doesn't have an X through it, Jeff figures that Nate passed the initiation and must still be alive... somewhere.