At some future point in time, Lydia has a vision of standing in fast-moving water. Dr Valack is guiding her through the vision and asking her to describe what she sees. It's night and she can see the bridge where a young Theo watched his sister, Tara, die. Valack urges Lydia to give him more and more details because he says he needs to know why Theo let his sister die.

Theo's sister rises from the water. She has a large gaping hole in her chest through which we can see her ribs. Her heart is gone. Once Lydia, with a fresh trepanation hole in her head, relates this news to Valack, the doctor speculates that Theo wanted her heart for a transplant to make himself a biological chimaera. He says leaving his sister to die in the cold water in hypothermic conditions would keep the organ viable.

The Dread Doctors are shown with the heart and a young Theo prepared for surgery. Valack doesn't understand why the DD wanted Theo, "A ten-year-old willing to kill his own sister." A groggy Lydia asks Valack why he cares. He explains that Theo was the first step in the right direction for the Dread Doctors. He explains they are para-scientists who have prolonged their lives and twisted the laws of nature in an effort to create the "perfect killer."

He says they've now reached that goal but Lydia says Theo doesn't know who their last chimaera actually is. Valack says that doesn't matter because there is a reason they chose Theo, a reason he failed and a reason they changed their methods and finally succeeded. Valack says it all starts with Theo.

~~~

Still in the future, Tracy disables an Eichen House guard with Kanima venom. Josh disarms one of the guards by grabbing his taser and absorbing the electricity from it. Corey becomes visible from where he had been camouflaged against the lobby wall. Orderly Schrader informs them that visiting hours are over. Theo joins his pack and says they are there for Lydia.

~~~

Dr Valack continues questioning Lydia. She says Scott and Stiles found out the Doctors succeeded on the night of the supermoon but that they didn't really know yet because there was too much going on. She explains the events of that night, Liam's attack on Scott, Kira's absence, Brett saving Selene, Malia's attempts to find the Desert Wolf and Sheriff Stilinski's injuries.

~~~

In the present, the Sheriff is wheeled into the operating room at the hospital. Dr Geyer, Liam's stepfather, says Stilinski has a lacerated liver and a perforated intestine. The Sheriff removes his oxygen mask and asks for his son.

~~~

Stiles is at the admissions desk where the person on duty can't seem to find the Sheriff's insurance information and mistakes him for a deputy which frustrates his son. Melissa arrives and takes control. She explains she texted Scott and he is on his way. She offers to call Malia but Stiles tells her not to call anyone. The person behind the desk asks if there is any next of kin she should contact. Stiles explains he's all the family there is.

~~~

Scott is caring for his wound in his bathroom. He drops a bloody rag into the sink. The wounds inflicted by Liam seem to have healed but the stab to his gut from Theo is still ragged and bleeding. He stares into the mirror and tries to spark his eyes. With great physical strain, he manages to get them to glow red briefly but they quickly flicker out and return to normal. He pounds the sink in frustration.

He retrieves some bandages from the medicine cabinet, gets dressed and exits his room into the hallway. His vision shifts and the hallway seems to warp away from him. He passes out and collapses to the floor.

~~~

At the hospital, Stiles sits in the waiting room all alone crying.

~~~

Parrish is in the shower. Dirt and pieces of charred leaves fall from his body. Suddenly Lydia is there. They kiss for a moment but then he notices that the nail of her right index finger is broken and bloody. He notices the dirt and leaves on the shower floor and questions what's happening. Lydia explains that he is a "harbinger of death" and asks, "Don't you know?" He doesn't and she says someone is dying. Parrish wakes up behind the wheel of an SUV in the middle of traffic. Horns blare as cars swerve out of his way.

~~~

Parrish calls Deputy Clark at the Sheriff's Station to let her know that Lydia is missing. She explains that he is missing too and says people there are really confused by his behaviour. He says he'll explain but tells her that she has to get everyone available to search for Lydia. She points out that there is a lot going down, recounting the attack on the school, the mostly trashed library and the fact that "there might be a prehistoric animal running around the streets." She also says she is thinking of transferring out of Beacon Hills. Parrish says he understands but he has to find Lydia. He leaves on foot and ends up in the woods near the Nemeton. He calls out for Lydia. His flashlight dies. He lights a flare and, as the flame passes near his face, his eyes flash orange and he sees something in the distance. He drops the flare and sets off.

~~~

Stiles is asleep at the hospital. He hears his father saying he needs to get up. As he returns to consciousness it is Melissa calling his name. She explains that the Sheriff came through surgery fine and he is going to make a full recovery. Stiles wants to see him but she says it will be two hours yet before the anaesthesia wears off. Stiles thanks God and begins to cry again.

~~~

Scott is unconscious on the hallway floor where he collapsed. Parrish wakes him and notices he is bleeding. Scott says it's not that bad and questions why the deputy is in his house. Parrish says he needs help and turns to show Lydia standing catatonic at the end of the hall. Parrish explains that he found her and Selene in the woods and Selene explains that she was practically hypothermic. Lydia had broken her nail and bloodied her finger drawing a sheriff's badge on a nearby rock. Scott says the badge is a warning.

~~~

The Sheriff is breathing heavily and raggedly through his oxygen mask. His skin looks dry and bruised.

~~~

Mason chases Liam from the school to the Sheriff's Station. Deputy Clark exits the building and takes one of the department's SUVs. Liam wants to tell her about Hayden's death but Mason stops him saying that looking like Liam does, bloodied and torn clothing from the fight with Scott, the authorities might think that Liam killed Hayden. Liam feels he might actually be responsible for her death. Mason says no. He says while the past few hours weren't Liam's best turning himself in to the police isn't the way to fix it. Liam suddenly smells Hayden's scent. She appears as a reflection on one of the car windows but the boys don't actually see her. Mason reminds him that he saw her dead body.

~~~

Scott, Selene and Parrish rush Lydia into the hospital emergency room. Scott makes for the elevator while Selene explains Lydia's condition to the doctors and nurses.

~~~

Upstairs, Scott sees Stiles becoming more and more upset as he talks to Dr Geyer and Melissa. He says his father is getting worse, that he was fine and now "it looks like someone took a baseball bat to his neck." Dr Geyer says there may be some minor internal bleeding. Stiles becomes more agitated as Scott makes his way down the hall and peeks in on the Sheriff in the recovery room. Melissa admits that they don't know what's wrong with the Sheriff. At that moment, Stiles spots Scott and runs down the hall toward him. He tackles him and screams at him demanding to know where he was while his father was getting attacked. He blames him for trusting Theo and demands again to know where he was.

Security guards separate the two as Scott explains that the Sheriff isn't the only one who got hurt. Stiles is dismissive and says, "You'll heal." Scott says he's not talking about himself.

~~~

Downstairs, Natalie is stroking Lydia's forehead and explaining that everything will be all right. Lydia turns away from her mother and toward the door a few seconds before Stiles comes in. Natalie freaks out on the boy, screaming at him to get out and blaming him (all of them) for Lydia's injuries. Stiles urges her to check the back of Lydia's neck. Natalie seems not to be listening as she forces Stiles from the room and closes the door behind him but she checks Lydia's neck. There are deep and ragged gashes from Theo's attempt to take her memories. Lydia begins speaking, repeating "I told you to stay in the car" which is what her mother told her when she wandered into Eichen House as a child and witnessed her grandmother's trepanation wound. 

~~~

"It could be a side effect of shock" Parrish says.

"She's catatonic. It was Theo digging his way through her mind" Selene says.

"Why would he do that? What is he looking for?" Melissa asks.

 "The same thing he's always looking for-" Scott says.

"- an advantage" Selene adds.

"So what did he gain by trying to kill Stilinski?" Parrish asks.

"It left me alone with Liam. Theo wanted to make sure no one would be there to stop him from... killing me." Scott explains and Stiles scoffs.

"Okay, so he gutted my dad as a distraction?" Stiles asks.

"We need to find this kid" Parrish says and Selene scoffs.

"Isn't that a little dangerous? Especially since he almost killed my kid?" Melissa asks.

"Yeah, but he said he didn't want my dad to die" Stiles explains.

"And you believe him?" Parrish asks.

 "He told me where to find him... So, maybe he also knows how to save him"

"What do you want to do? Talk to him?" Melissa asks.

"If it saves my dad, then yeah" Stiles responds.

"I'll come with you. He doesn't know that I'm alive-- maybe that gives us an advantage" Scott purposes.

"Absolutely not. He'll know you're there. I just need to talk to him, not fight him" 

~~~

As the sun comes up Theo finds Stiles at Scott's house. There is a line of Mountain ash across the doorjamb but Theo crosses it with ease since he is a chimaera and not supernatural. 

~~~

At the hospital, Natalie Martin holds an admission form that will send Lydia to Eichen House. Conrad Fenris assures her that Lydia will safe there because Eichen is a "very different place now." Natalie signs the form. Parrish exits the elevator and calls out to her. He catches up to her and asks about Fenris and where she's sending Lydia. Natalie says she did what she had to.

~~~

Scott is upstairs listening to Stiles and Theo's conversation. Theo's eyes drift to the top of the stairs as if he senses the Alpha's presence. Stiles throws Scott's torn and bloodied shirt to Theo saying, "You killed my best friend." Theo questions their friendship but Stiles changes the subject and asks if Theo plans to let the Sheriff die. Stiles explains that some toxin is poisoning the Sheriff. Theo denies knowing about it saying he's not "the bad guy." He says he's a "realist" who knows what's coming, what the Dread Doctors created and what Parrish is.

~~~

Liam and Mason go to the hospital to question Dr Geyer (Liam's stepdad) about any bodies that might have been brought in. They're looking for Hayden. Dr Geyer says there have been none and asks Mason to take his stepson home since it's 6 in the morning. The boys figure out that they need to find the Nemeton to find Hayden's body.

~~~

Theo tells Stiles that he saw that Parrish is a Hellhound in Lydia's memories. Theo calls Lydia's catatonic state "collateral damage" and says things are going to get a lot worse. Stiles says he doesn't care. Theo says if the elder Stilinski does survive he won't be Sheriff of anything much longer. Stiles demands to know what's happening to his father. He rushes Theo who easily throws him back on the stairs where Stiles' head hits the wood and he is knocked unconscious. Again he hears his father's voice and sees his face saying "Stiles you need to get up. You've got to get up now."

Scott is standing over him as Stiles wakes. He brushes off Scott's extended hand. He wants to know if Scott sensed anything while Theo was talking. Apparently, the chimaera's heart rate jumped briefly when Stiles explained that his father was poisoned. Stiles takes this to mean that Theo was surprised to learn the Sheriff is still dying. Scott posits that Theo didn't attack his father and that something else did.

~~~

In the hospital, Sheriff Stilinski is laying in bed and weakly whispers something. Selene, who was in the room to check on him, hear this and her eyes flash their Kitsune colour for a second.

~~~

Scott follows as Stiles climbs into an SUV and locks the doors. Stiles says he doesn't need any help. Scott says he can help find the clues that Stiles can't and places himself in front of the car. Scott says Stiles needs the whole pack's help and offers to text Liam. Stiles points out that Liam just tried to kill him. Stiles is still upset that Scott believed Theo's lies about how Stiles killed Donovan. Scott points out that Stiles trusted Theo's lies too. Stiles says Scott still doesn't know the real story. Scott says he doesn't need to. He says all that matters right now is Stiles father. He points out that they survived an Alpha pack, a dark druid, and professional assassins so they can survive Dread Doctorschimaerasmeras too. This last bit sparks a thought in Stiles. He realizes that they're not looking for a missing chimera, they're looking for a missing teenager.

~~~

Mason and Liam go to the school library to look up a map of the ley lines reasoning that the Nemeton would be at one of the spots where the lines cross. Liam flashes back to his fight with Scott the night before reliving much of it as he walks through the ruined library. Liam explains that finding the Nemeton is a near-impossible task because the supernatural tree has to want to be found in order for people to see it.

~~~

Parrish watches as Lydia is loaded into an ambulance. Natalie gets in with her. Parrish promises that he'll find a way to get her out of Eichen House even if he has to break through the walls. Fenris wishes him good luck with doing that. As he gets into the ambulance his reflection shows that it is not Fenris at all, somehow Dr. Valack was able to change his appearance to look like the other Doctor. Orderly Schrader is behind the wheel of the ambulance and points out how attractive Lydia is. Valack points out that Lydia could shatter his skull with her voice if someone taught her how.

~~~

In Stiles room, he and Scott review police calls about a missing sophomore named Noah Patrick who didn't come home last night. Noah is on the list of natural chimera's that were potential subjects for the Dread Doctors.

Scott breaks into Noah's locker at school and retrieves a shirt so they can track his scent. Malia shows up. Stiles doesn't seem happy but Scott says he should be calling everyone. Malia points out that she knows what Noah looks like.

~~~

Noah runs through a warehouse loading bay, looking over his shoulder as if something is chasing him. As he hides behind a concrete barrier, he hears and then sees the Dread Doctors approaching.

~~~

Mason and Liam wander the woods. They've found the intersection of ley lines on the map but can't find the Nemeton. Liam laments that he couldn't save Hayden. Mason says no one could and recounts all Melissa's efforts to keep her alive. Liam expresses guilt over trying to kill Scott but Mason points out that there were "like 800 extenuating circumstances" including but not limited to losing Hayden, fear, anger, and Theo. He also points out that Liam is a werewolf and there was a supermoon. This sparks an idea.

Mason figures if the stump acts as a supernatural beacon then Liam should be able to see it if he looks with his werewolf eyes. He does and spots the tree. Mason still can't see it until Liam puts his arm around him and guides him to look in the exact spot.

~~~

Scott, Stiles, and Malia arrive at the warehouse where Noah was hiding. Malia says she and Stiles "kind of broke up." Scott says he and Stiles broke up too. Scott says Malia can talk to him if she wants. She says she's only there to help find the kid and save Stiles' dad. Malia catches Noah's scent.

~~~

"Melissa, that man in there is dying, and I don't know how to save him. I went to Harvard Med. I have degree lining the wall of my office. And I don't have the slightest clue what's going on here" Dr Geyer says. Melissa's expression is both worried and slightly guilty and uncomfortable, which doesn't escape Dr. Geyer's notice. "If you know something about this that I don't..." 

"Me?" Melissa tries to play dumb, but even she knows her response isn't very convincing.

"Yes, you. Nothing seems to faze you. And, not to sound accusatory, but it's like you know something" 

"Knowing something is different from understanding it<>"Dr. Geyer looks at her with confusion, as though he's debating whether or not he wants to know what she knows.

"Yeah, I could tell you things-- really bizarre things. But, right now, I can't tell you anything that is gonna save his life"

"I can" Selene says walking up to them.

"What do you mean?" the doctor asks.

"I'll explain how I know later but right now, you gotta open him up"

"Selene we can't jus-"

"Do you want to save him or not" the doctor nods. "Then you gotta trust me and open him up"

~~~

Mason and Liam count the bodies around the tree but only find four. Hayden isn't among them. Liam believes this means Hayden is alive. Mason suggests they get the cops and at that moment headlights flash on and Hayden leads a group of deputies in claiming she found the bodies.

~~~

Scott, Stiles, and Malia are searching the tunnels for Noah. Scott realizes that these tunnels look like the tunnels they searched under the water plant when they were looking for Hayden and Liam. Stiles doesn't care. He goes off on Scott about wasting time while his dad is dying. Noah jumps out of the shadows and attacks Stiles, driving his head into the concrete and knocking him unconscious.

Once again Stiles hears his father's voice urging him to get up. He remembers being a child at his mother's funeral and his father telling him that he would have to get up from where he was kneeling by her casket. In the memory, Sheriff Stilinski tells his son that, "You still got me."

~~~

Scott helps Stiles to his feet. Malia and Noah fight but she gets the better of him quickly. He transforms and begs for mercy. Noah warns them that the Dread Doctors are coming. They approach slowly from the tunnel. Noah runs away but Stiles catches him. The chimaera says he doesn't remember anything when he is transformed. Stiles explains that the boy clawed his father half to death and he's now dying from poisoning.