Theo grabbed Lydia and placed his claws to her neck. Josh was holding Molly hostage.

Tracy growled at Parrish and began running toward him. She attempted to thrust her claws into his stomach, but he threw her against the wall. Josh threw Molly to the ground and tried to do the same with a set of electrical conduit wires towards Parrish, and was also shoved into the wall. Valack plunged a trepanation needle into the back of Theo's thigh.

Valack grabbed Lydia and Molly and turned to leave. He rushed out with them and Stiles stepped in front of them to block them. "Hey! Lydia! Molly! Lydia! Molly!"

Stiles managed to grab Molly and swept her in his arms.

Parrish threw a flaming Corey, knocking Stiles back, and allowing them to get by. Stiles managed to roll Corey off and chased after Valack and Lydia, but was stopped by a locked door.

Sam and Dean followed the sounds of the fight and ran up as soon as they saw their sister. Sam glanced at Dean and said, "Get her checked out."

Dean nodded and Molly tried to stand, but collapsed in Dean's arms. He picked her up and left, giving Stiles a nod.

Stiles turned and tried kicking the door to run after Lydia and Valack and heard Theo say, "Let me try. You're not gonna find her without me."

Sam narrowed his eyes and said to Theo, "You're lucky we've got a missing teenager to save."

"Stiles," Theo called again. "I want her out of here, too. I've got her scent."

"What do you want?" Stiles snapped.

"What's the difference?"

Stiles scoffed. "Huh."

"I can find her. You can't." His eyes glanced over to a vent that had steam blowing from it. "It leads to the tunnels, doesn't it?"

Stiles nodded. "There's miles of them. They could be anywhere by now."

---

Lydia was screaming in Meredith's mind. Meredith turned to Scott. "She doesn't have much time."

"What's happening to her?" Scott asked in a worried tone.

"She's being consumed by her power. Dr. Valack thinks it's worth it if she can answer the question."

Scott raised an eyebrow. "What question?"

"Who is the Beast?"

"She can answer that?"

Meredith shook her head. "Not yet. Not until the screams in her head are loud enough to kill her."

Scott instantly panicked. "How do I get to her?"

"You can't. You won't be able to get past the Mountain Ash. But someone else might be able to."

"Who?"

"The Hellhound."

"You mean Parrish?"

Meredith nodded. "Find the Hellhound... and he'll find the Banshee. The huntress has been freed."

Scott removed his claws from Meredith's neck, but not before hearing one last whisper. "Save her."

The door opened to reveal a very large muscular guard staring at Scott before falling down to reveal Liam with a fist in the air. "Oh! Is he out?"

Scott nodded. "Yeah."

"Okay," Liam said before collapsing.

---

Stiles frowned at Theo. "I thought you had her scent."

"I lost it."

Stiles' eyes narrowed. "So find it again."

"What do you smell down here?"

"Chemicals and fecal matter. Although, I'm pretty sure the fecal matter is you."

Sam frowned. "Cut it out. Theo, where is she?"

Theo rolled his eyes at Stiles' insult. "I smell it, too. It's all that I can smell. Which is why I'm trying something else. So can you shut up and let me concentrate?"

"I'm gonna find her. With Sam's help."

Theo shook his head. "You know you won't, Stiles. You're going to have to trust me."

"Trust you? The guy who murdered his own sister when he was nine?"

"Yeah, I was nine years old. I also believed a guy in a red suit came down the chimney to deliver presents. So when three people in leather masks showed up and said that my sister wanted me to have her heart, I believed them, too."

"So then together you gutted and killed her. That's a beautiful story."

Theo's expression hardened. "I watched her fall into the water and freeze to death in minutes. Do you think I had any idea what was going on?"

Stiles narrowed his eyes. "I think you pushed her. And I think you liked it."

"Enough!" Sam yelled. "We have an injured teenage girl to find. So stop your arguing and find that girl!"

In that moment, they heard a very distinct scream. Stiles whipped his head in the direction he thought the scream was coming from. "What direction was that? Where is it coming from?"

"Everywhere," Theo answered.

---

Lydia was strapped down to a chair, hearing a plethora of screaming in her head. Dr. Valack said to her, "Just hold on a little longer, Lydia. You can make it. I want you to focus on this, Lydia. And what other sounds you hear now, push them aside." Lydia attempted to do so as Dr Valack turned on a device emitting an electronic hum.

"Focus on this sound. That's it. Focus on this sound and my voice. All right, Lydia." Lydia gasped, seeing Nurse Cross. "Don't worry, Lydia. Nurse Cross wasn't nearly as strong as you are." Electricity began crackling and Lydia continued to whimper.

Scott and Liam found Deputy Parrish lying in a stairwell. "Parrish? Parrish," Scott called. "Parrish. Parrish, hey. Can you hear me?"

Parrish looked up at Scott. "How did I get here?"

Scott shook his head. "We don't know. We just followed the burning smell. Parrish, listen. Eichen's in lockdown. There's no way for us to get out unless Plan B works."

"Plan B? What's Plan B?"

"Don't worry about it. Right now, we need you to find Lydia."

"Me?"

"Actually, not completely you," Liam admitted. "We kind of need the other you."

Scott nodded. "The Hellhound."

Meanwhile, Malia and Kira nursed Josh and Corey, who wasn't healing. "Why isn't he healing?" Josh asked.

Malia shrugged. "Maybe he can't. Maybe it's too much."

"Or maybe it's the pain," Josh guessed as Corey groaned. "He's going to die, isn't he?"

"His heartbeat's getting slower."

"What do we do? You can't heal him, can you?"

Malia shook her head. "No, but I can take his pain. It could help. It might even get him to start healing."

"Then do it."

"You first."

Electricity began crackling and Malia narrowed her eyes at Josh. "You said you could help her."

"Yeah, but it's not like taking voltage from a car battery. She's got a lot more power than that. Are you going to do something or not?"

"When you help her," Malia decided. "I don't trust you."

"I don't trust you either."

"All right. We go at the same time."

"You ready?" Malia asked as Josh nodded. "All right, here we go."

Malia grabbed Corey's burnt arm and black veins appeared, letting her absorb Corey's pain. At the same time, Josh grabbed Kira and his body was immediately surrounded by purple lightning as he roared.

---

Stiles groaned. "Nothing. Great. You're just as useless as I am."

"I'm trying to help save her life," Theo retorted.

"Would you just drop the altruistic crap? You want Lydia because they get you to Parrish, you want Parrish 'cause he gets you to the Beast."

Theo shrugged. "So what? I want it dead, too."

Stiles narrowed his eyes. "After you take its power, right? We know why you got the talons and we know you're looking for Deucalion."

"I found Deucalion. You're right. I'm going to help Parrish stop the Beast. I'm going to take its power. And then I'm going to break its neck. So maybe I'm not the good guy in your eyes, but I might end up being the guy that saves all your asses."

"Break it," Stiles and Sam ordered.

"What?"

"The sound travels through the pipe," Stiles told him. "You'll hear better, dumbass. Break it."

Theo did so and they heard Dr. Valack say, "Lydia? Can you hear me?"

"What do you want from me?" Lydia asked.

---

"I want your help against the Dread Doctors. They ruined me. Destroyed me. They drove me to obsession, consigned me to professional ridicule. People thought I was a monster when I was simply trying to open their eyes."

"Now you want her to be your eyes," Lydia retorted.

"You'll see things Lydia. Things no one else can see. You may not survive, but you might save the lives of your friends." Valack pulled out the Dread Doctor mask.

Lydia yelled, "Do it!"

Valack continued. "We have to slow your mind first. There's too much activity in your brain. We have to get from a gamma wave to a theta."

"It's too loud! I can't!"

"If I try the mask now, it will kill you. You have to calm your mind. You understand what they've created."

"The Beast."

"The Beast of Gévaudan. An engineered version of it. But it's not yet fully grown. It's still bound to its host, the teenage Chimera inside. And it still requires the Dread Doctors' protection."

"Damnatio Memoriae."

Dr. Valack nodded. "That's right. The Beast was a man first. A human killer in the late 1700s. The Dread Doctors are trying to get it to remember itself. To remember the man. When that happens, the teenager is gone."

---

Josh helped Corey off the morgue table. He was healed, besides blackened parts of his skin. "Anybody know how we're supposed to get out of here? This place is still in lockdown."

Malia shook her head. "It's not just locked."

Josh nodded. "Yeah, I can feel it too. What are we supposed to do? Just wait here?"

"There's a Plan B. We've got a guy on the outside in case this happens."

"Who?"

"Mason."

Josh scoffed in disbelief. "Mason's going to unlock the lockdown? How's he going to do that?"

"He's got the blueprints of the building. And he has the full map of Eichen's electrical system. All he has to do is get into the transformer shed behind the building. Don't worry. Mason knows exactly what he's doing."

Outside Eichen House, Mason was panicking as he left a voicemail for his best friend. "Liam, call me back, I have no idea what to do. And I'm panicking. I'm completely and totally panicking. I drove around this building, like, four times and I can't find this transformer shed. Well, actually, that's partially right. Because I found where the transformer shed is supposed to be. But it's not a shed anymore. It's a wall. Like, a very big wall. So, I mean, I tried calling Hayden. And she still isn't here, and I heard alarms go off. Now I don't know what to do. So, Liam, just call me."

---

Stiles, Sam and Theo began zeroing in on Lydia.

---

Dr. Valack explained to the girls, "This teenager, Lydia, is the last Genetic Chimera. A young man or a young woman, maybe even someone you know. A success where Theo and the others were failures."

Lydia frowned slightly. "But we went through the list of Genetic Chimeras. There's no one else."

"There must be one you missed. Another way they could have two sets of DNA. If you could see the face of this teenager, discover its identity, then your friends would have a fighting chance. This mask can help you see."

Stiles, Sam and Theo arrived outside the laboratory and began banging on the door.

"Lydia!!" Stiles cried.

"Lydia!" Stiles yelled again. He turned to Theo. "What the hell are you going? Get the door!"

"I'm trying!" Theo retorted.

The machine Valack had been using to calm the screams in Lydia's head began sparking and shut off. The screams came back, seemingly louder, and Lydia began losing control. Valack picked the mask up. "I'm sorry. But time's up." As he came close to her, Lydia screamed. The mask fell out of Dr. Valack's hands and half his head became a bloody pulp.

Theo broke the door handle and Sam immediately rushed in.

Sam saw Lydia in an operating chair. She looked like she'd been through hell.

"You came back," Lydia said softly, noticing Stiles.

"We're getting you out of here, okay?" sam told her.

"No. It's too dangerous."

"Lydia, let me save your life."

Sam helped Lydia up and they began walking slowly.

"The plan didn't work out too well," Stiles admitted. "So Sam and I are gonna need your help, okay?"

Lydia looked up at Stiles. "You had a plan?"

He nodded. "Yeah. It was good on paper. Not too much in reality."

Lydia stopped abruptly. "I can't hold it."

Lydia slumped to the floor and Stiles and Sam called, "Lydia..."

"Stiles, Sam, run!"

Scott and Liam pulled Stiles and Sam away just as Lydia screamed. Moments later, they saw Parrish coming out with Lydia.

"Where to?" Parrish asked.

"This way." Scott ran down the hall. "Come on."

"There's a gate up ahead," Liam informed.

"What about Mason?" Scott asked in a doubtful tone.

"He's on it. Trust me," he reassured as he ran faster.

"Liam, slow down!" Scott warned.

"Liam, wait!" Stiles yelled.

Liam grabbed the gate, causing it to spark, but he pried it open. "I told you."

They made their way outside the gates and Malia and Kira arrived in the Jeep.

"Is she okay?" Malia asked.

Scott shook his head. "No, we need to go. Give me the keys. We gotta get her to the clinic."

Parrish groaned and fell against the car. Tracy grabbed Lydia and held her claws to Lydia's neck. "Sorry, but she's coming with me."

"Okay, Tracy, just wait," Scott pleaded. "You don't know what's about to happen."

"I'm taking her. That's what's happening. And none of you are going to do a thing..."

She was cut off as Ms. Martin came over and shocked Tracy with a taser stick. "Could somebody please get my daughter out of this hellhole?"

Stiles got into the back of his Jeep. Lydia rested her head on Sam's lap. Sensing Lydia was getting worse, Stiles warned his friend. "Scott."

Scott was still working on the Jeep. "Yeah. I'm trying, I'm trying."

"Just hang on, okay, Lydia?" Sam said. "Hang on."

Lydia let out a small scream. A mirror broke and Stiles and Sam felt their ears bleeding. Scott had gotten the Jeep started and began flooring it.

Sam looked worriedly st the teenage girl. "Hey. Lydia, Lydia, hey, hey, hey, hey, hey. Look you are gonna get through this, okay? Lydia, you're gonna make it."

"But you're not," Lydia whispered.

They rushed the the Animal Clinic. Deaton looked at them. "Get her on the table."

They placed Lydia on the table. Lydia let out a high-pitched shriek.

Whoa, whoa, whoa," Stiles said.

"Hold her," Deaton ordered.

"Doc, think you gotta do something," Stiles warned.

Deaton nodded. "I will. But right now, I need you to keep her still. Steady. Steady." Deaton held a syringe of liquid.

"What the hell is that?"

"Mistletoe," he answered.

"Mistletoe? She's got a fricking hole in her head!"

Deaton looked to the panicked teen. "Stiles, help. Robin, some help from you, please. Steady." Simultaneously, he placed the syringe in Lydia's head, causing her to let out an ear-shattering scream.

Stiles and Sam fell to the floor and when it was quiet, they saw her lying unconscious on the table.

Sam shook the strawberry blonde. "Lydia? Lydia. No, no, no, no, no. Come on, Lydia. Wake up. Come on. Wake up. Can you hear me? Lydia. Open your eyes. Come on, come on. Come on. Listen to me. Hey, show me your eyes, Lydia. You have to open your eyes." She noticed Natalie Martin near the entrance He hoped he didn't have to tell her the worst news a parent could hear.

Lydia slowly opened their eyes and Sam let out a relieved sigh. "Oh, thank God."

Scott walked over to Lydia. "Want to try to sit up?"

She nodded and he helped her sit up.

Lydia glanced to the door. "Mom?"

Ms. Martin rushed over. She embraced her daughter. "Oh, honey."

Lydia met her mother's eyes. "They saved Molly's and my life, Mom. Our friends saved us."

Stiles smiled awkwardly. "I'm not paying for the windows."

Ms. Martin took Lydia home.

Dean walked in with Molly who instantly rushed to her friend and hugged him tightly.

Sam stepped closer to his brother. "Lydia will be okay. Looks like Molly will too."

Dean nodded. "She's tough."

Stiles tucked Molly's hair back and asked, "Are you okay?"

She nodded. "Yeah. Thanks for getting my brothers here."

"They're family." She smiled and hugged him.

Stiles hugged her back, glancing at Sam and Dean before quickly pulling away.

Molly laughed, then shot her brothers a look and they smiled innocently.