At some point in his adult life, he had an encounter or extended history with the Dread Doctors, which disturbed him so greatly that he wrote a novel titled The Dread Doctors, which was meant to act as a tool to help those whose memories had been suppressed or modified by the Doctors to trigger the memories in the form of flashback-hallucinations. His intent was that someone who had been experimented on or had their memories tampered with by the Doctors would read the book, begin to have their memories resurface, and would then seek him out to learn more. However, only one copy of the book was ever printed.
During his career as Chief Medical Officer of Eichen House, Valack became enamored by the supernatural and began to perform his own experiments on those in the facility's supernatural ward by using the ancient practice of trephination, or drilling a hole into a patient's skull. Valack performed trephination on every supernatural creature he came upon, including werewolves, banshees, and wendigos. These experiments initially amplified their powers, but the powers' intensity eventually grew so great that it would kill them. This was particularly true of banshees, who would hear the screams of every dying person on earth until they finally foresaw their own deaths and died while wailing for themselves.
Dr. Valack is behind a plexiglass wall in his cell. He says that Deaton must be important because they don't usually let people get this close. Valack complains that while they let him read, all he gets are trashy romance novels. He tosses the one in his hand onto a pile on the floor. Valack recognizes Deaton by name and says he knows his specialty is not cats and dogs. Deaton says he's there because of what Valack knows about South American mythology, but Valack says he's there to learn about Kate Argent. "You want to know about La Loba. The Bone Woman." Deaton looks thrown for a moment. "I need to know what she did to Derek Hale. And if he's dying." "Why?" "Because of a promise I made. To a woman I loved." Valack tells Deaton to come close, but Deaton replies that he's been advised against it. He's only there to talk, to hear what he knows. "You need to see what I know," Valack says. He removes a band of cloth from around his head revealing a hole. Deaton looks distressed and says that just because Valack trepanned himself doesn't mean he's given himself extra-sensory perception. Deaton looks at the hole and is drawn to it. Valack urges him on, and Deaton seems to move against his will, staring at it. Inside Valack's head, a third eye opens.
Peter is delivered to Eichen House. They put him in cell 8, which happens to be the same cell as Valack. Peter is clearly drugged. "You actually think this is gonna hold me? You think you can shoot me up with wolfsbane, make me docile and weak and I won't find a way out!" He pants in anger and leans against the plexiglass wall. "It's not just the wolfsbane. It's the mountain ash wood framework of the cells," Valack says helpfully. Peter turns to look at him and asks who the hell he is. "I could tell you, but it's easier if I just show you," Valack says. Valack removes the bandage over his third eye, and Peter stares into it. When the third eye opens, Peter turns around and throws himself at the wall, screaming.
Valack asks them what they just saw in the previous cell. "The slaugh. The myth is that they can take on the appearance of the lost souls that have become inextricably bound to it. Happened to see any lost souls, Mr. Stilinski?" "Yeah, everyone down here," Stiles responds. Valack tells him not to give up on them yet. "We're all works in progress." It's something Peter says. Lydia recognizes it and asks him where he heard it. "Wise words from a former cell mate." Valack asks if they brought the book, and Stiles shows him the copy. Lydia realizes there is no T.R. McCammon. Valack wrote the book. It's a tool designed to open their eyes. Lydia asks VAlack why he used a psuedonym. He claims he had a professional reputation once and didn't want to ruin it by putting his name on a second rate piece of trash. "Then why write the book in the first place?" Stiles asks. Valack explains taht he wrote it because no one believed him, no one listened. He knows the Doctors are in Beacon Hills. "What are they?" Lydia asks. "Not entirely human. At least not anymore. They were scientists once. Scientists who worshipped the supernatural. Teska said, 'If you want to find the secrets of the universe, think in terms of energy, frequency, and vibration.' They found their secrets in electromagnetic forces. Ways to prolong their lives. Give them power. And most importantly, making you forget you ever saw them." Lydia asks what they want. Valack tells her it's a good question, because everyone wants something. Stiles realizes it's the start of his request and asks Valack what his price is. He wants a recording of Lydia's scream. Stiles takes the recorder away from Lydia and declares that Valack is not getting his recording. Lydia doesn't agree and wants to do the trade. While they're talking, Valack asks them how many have died so far. He asks if they want to know how many died the first time the Doctors came to Beacon Hills, or how many will die if they succeed. "This did happen before," Lydia says. "And now they're back. All because a few teenagers who never even considered the consequences decided to reignite a supernatural force they barely understand." Lydia realizes he's talking about the nemeton and the sacrifices they performed. Stiles asks how he even knows about that, and Valack replies that he knows because he saw it. He removes the band from his head, and Lydia looks into his third eye. Valack sees the lights flicker and asks who they came with. When they don't answer, he knows they brought a kitsune. A light explodes. Kira is disrupting the building's defenses. "It's not just the mountain ash that keeps this building secure. It's the electromagnetic energy. Eichen is built on the convergence of telluric currents. Ley lines. IT's what allows it to keep certain supernatural creatures in and certain others out. They knew you were coming. They're here. And you unlocked the door for them." Valack orders them to hit record and give him a scream, because it costs them nothing. Stiles replies that it's important to him so he's not getting it for free. Lydia asks what the book does. He explains that reading the book opens their minds to the memories that the Doctors repressed. The book was meant to trigger peoples' memories. And then those people would find their way to him. Lydia recalls having flashes of the doctors while she was on the operating table. "If you've seen them, if they've done something to you, then the book will help you remember. Now give me what I want!" Lydia holds out her hand for the recorder. Lydia asks Valack what the Doctors are trying to do. He just tells them all to read the book, anyone who has come in contact with them should read it. Stiles rushes to get out of there. The Doctors go to Valack's cell. They hold him down and pluck out his third eye. Valack crawls to the door of his cell and puts the recorder in a cup. He holds it against the glass and plays it back. Lydia's scream cracks the glass. 
After escaping from his cell, Valack takes over Eichen House. After finding out that Lydia was comatose, he discusses himself as Dr. Conrad Fenris and visits Lydia's mother at the hospital with a offer to move Lydia to Eichen House. When Natalie signs the documents, Valack moves Lydia into the back of an ambulance and drives off with his other collogue.
After waking up from her coma, Lydia escapes from her cell, Valack confuses her by making himself look like Aiden, her lost love. At the gates of Eichen House, Valack (disguised as Aiden) appears to Lydia as if an hallucination. Lydia stops and the other guards grab her and take her back to her cell. In her cell, Valack treats her injuries and asks her what happened to her friends and she faintly remembers a fight between Scott and Liam, strange looks from the Sheriff and Melissa, Kira leaving, Parrish turning into something else, Malia succumbing to the desert wolf and Stiles lying unconscious outside of his overturned truck. When she fails to give the doctor information he prepares to drill into her head for a lobotomy.
After amplifying Lydia's abilities, Lydia finds herself wading in a river near a bridge. Dr. Valack is asking her to describe what she finds and to tell him what "he" did. She digs deeper in her dream as she is asked why whoever he is let a girl die. A corpse rises up from the water and grabs Lydia. The corpse is missing a heart and it's made clear that Theo let his sister die in order to get her heart transplanted into him by the Dread Doctors. He was the first step in the direction that the Dread Doctors was going in.
Valack shows his assistant the mask he used on victims and it looks like the same mask the Dread Doctors wear. He tells her to close the door and tries it out on her. She screams in pain and collapses to the ground. In Lydia's cell, Valack tells Lydia that he amplified her abilities. She tells Valack that they found the symbol of Scott's pack and that someone is coming. However, it's not Scott, it was Theo and his pack of chimeras. Theo and a couple of his chimeras attack Dr. Valack and he makes his way over to Lydia. He instructs the chimeras to pick her up and get her out. Valack is being held up by Theo who says he is looking for a hellhound and just then Parrish is shown in flames, anger and melting the cage down.
Parrish is walking towards the chimera's, Theo, Valack and Lydia. Theo warns Parrish to back off but he doesn't. When Theo sends his pack against Parrish, they all are taken out with ease. Valack drills into Theo's leg when he is distracted and takes Lydia away to another hidden part of the facility. Valack is continuing his experiment on Lydia trying to increase her frequency. He tells her to focus and push all of the sounds except the one frequency aside. She seems to be doing fine but when she looks over, she sees the body of nurse Cross. Valack tells her not to worry because nurse Cross wasn't nearly as strong as her. Valack wants Lydia to help him take out the Dread Doctors for humiliating him and making him look like a monster. He says he was simply trying to open the eyes of other people. He wants Lydia to be his eyes because she can see things other people can't. He tells her that she might not be able to survive, however, she can say the lives of her friend. Valack is trying to get Lydia to calm her mind or else she can die from what Valack has created. The doctors created the beast of Gévaudan and the Dread Doctors are trying to get it to remember it's legend, rather than the teen inside. Valack tries to get Lydia to identify who the beast of Gévaudan is. Theo tries to interrupt the process and manages to do so. Lydia kills Valack with her scream.