At Duke, everyone was still going through the information. "Any luck?" Damon asked.

"Nothing in here about Katherine that you haven't told us." Jeremy told him.

"Well, it's not like she kept her life out there for the public to see."

"You're the one who dated her." Jeremy pointed out. "Is there anything you know that can help us?"

"Hey, guys! Check this out." Alaric called. They went over to where he and Vanessa were talking.

"There's no record of werewolf mythology in Mystic Falls but here are some records of some the lesser known legends." Vanessa told them. "Everything from Scandinavian skin walkers to Aztecs legends." She opened the book to a page with symbols drawn on it. "It translates into the "curse of the sun and the moon"."

"It's Native American."

"Aztecs." Vanessa corrected. "It explains one origin of the werewolf curse traced through Virginia. The short story: 600 years ago, the Aztecs were plagued by werewolves and vampires. They terrorized the countryside, made farming and hunting impossible until an Aztec shaman cursed them, making vampires slaves to the sun and werewolves servants of the moon." The guys looked at her and she continued.

"As a result, vampires could only prowl at night and werewolves could only turn on a full moon. When the full moon is crossing the sky, who's ever unlucky enough to fall into the werewolves curse turns into a wolf."

"Can they control it at all?" Damon asked.

"If it were a choice, they wouldn't call it a curse." Vanessa said.

"Even I know that." Jeremy said.

"Werewolves will attack humans," Vanessa explained. "but instinct and centuries of rivalry have hardware them to hunt their prey's choice: vampires."

"If werewolves were hunting vampires, why haven't we heard about it?" Alaric asked.

"Hundreds of years ago, vampires almost hunted them to extinction." Vanessa told him.

"Why would they do that?" Jeremy asked.

"To protect themselves. According to the legend, a werewolf bite is fatal to the vampires." Vanessa said. Jeremy and Damon looked at each other.

Back at the swimming hole, everyone was starting to leave. It had gotten dark out. "He's mad at me." Caroline said.

"Go talk to him." Elena said. "We'll be right here if you need us." Caroline walked over to Matt, when her phone started ringing. "Hi."

"Hey, I think we found something here that's not going to sound good."

"Just tell us." Stefan noticed Caroline and Matt walk away.

"You better be careful. It's a full moon tonight." Jeremy was saying.

"I will be." Elena said.

"Yeah, you'd better. The legend says a werewolf bite is fatal to a vampire." She looked around. "Hey, where'd Caroline go?"

"She and Matt went into the woods." Stefan told her. "What's going on?"

"Jer, I'll call you when I get home." Elena said. She hung up. "Stefan, you need to leave. I'm going to get Caroline out of here."

"Elena…"

"Stefan, they found out a wolf bite's fatal to our kind." She said. "I'm not going to let my friend get killed because of me. I'm going to find her, you just get out of here."

He headed for the car, to her relief. Then she took off into the woods.

Back at Duke, the others were still looking around. "Have you done any research on doppelgangers?" Jeremy asked.

"The word means many different things, but basically it's like a double of someone." Vanessa said.

"True, but that doesn't explain why they look alike." Damon said. Vanessa turned to him.

"We think that my sister is somehow connected to Katherine." Jeremy explained.

"Well, I don't know how they'd be related. All I know about doppelgangers is that they usually torment the people the look like, trying to undo their lives."

"In other words, nothing we haven't been able to find on Google." Jeremy said.

"All I know is that there's a missing link here."

"Are you sure you don't know anything that can help her?" Jeremy asked. Then he started to leave. "Never mind, I forgot who I was talking to." He left the room.

At the car, he had trouble getting the door. "It's locked, you know." He turned around.

"No kidding."

"Just thought you might want to give this to your sister." He handed him a book. There was a name on the side.

"Petrova?"

"Katherine's family was from Europe. It's her real name." He explained. "Or maybe her ancestor's."

"How do you know that?"

"I saw the name engraved on the back of a locket she used to wear." Damon told him. "This book should have some clue on how their related, if not, her family history."

"You know I still can't stand you." Jeremy said. "But I appreciate the help."

In the woods, Elena was running. She'd tried calling her cell phone, but she wasn't answering. She was listening closely, when she heard what sounded like a growl. "Did you hear that?" She heard Matt ask. She sped over to where he and Caroline were.

"Caroline, we really need to get out of here." She told her.

"What's going on?" Matt asked.

"You know all those animal attacks?" Elena asked, trying to warn Care and not blow their secret at the same time. "Well, if we don't get moving, we're going to be their next target!" She told them.

"Wait, we can't just leave him." Caroline said.

"Stefan has the car, he can help him." Elena said. "Right now, we need to run!" Suddenly, they heard the sound of something moving. "Matt, if you take the south trail, you'll find him there. Go, now." He took off.

"Okay, we're going the opposite direction. Run as fast as you can." Elena told Caroline. "It'll get it off Matt's trail." Caroline nodded, understanding. "Okay, run, now!" They both took off but stopped near the ruins.

"Wait, what's after us?" Caroline asked.

"A werewolf." Elena said. "It has the ability to kill us and it will try if it gets close enough." Caroline looked at her, horrified.

"Hey, what are you girls still doing here?" Tyler asked.

"What are you doing here?" Elena countered. "I thought you left."

"I saw something in the woods," He began. Just then, a wolf rushed out and jumped onto Caroline. Elena pushed it off of her. Caroline was still on the ground and Elena wasn't sure she could take a wolf in a fight.

"Stop!" Everyone turned to look at Tyler, including the wolf. Then, it ran back off into the woods.

"Are you really okay?" Caroline asked. Elena had returned her phone and she was checking in on Matt.

"Yeah, Stefan picked me up right where Elena said he'd be."

"Thank goodness."

"Are you okay, Care?"

"Yeah, I was almost attacked, but Elena saved me." Caroline said. "I'll see you tomorrow. Bye."

"Okay, I'll meet you later." Elena hung up. The girls sat together.

"You think Tyler saw that?"

"As far as I'm concerned, he probably thought it was just a normal wolf." Elena said. "We're likely in the clear."

"I can't believe this."

"You're just going to have to work harder." Elena said. "Who knows how many others there are?"

"I shouldn't be with him, should I?" Caroline asked. "Because if there is any danger…"

"I know, it's hard." Elena told her. "But I can tell he's still into you. It's your decision, though, Care. I would've walked away from Stefan long ago if I had to."

"Do you ever think you should?" Caroline asked.

"All the time, but I can't." Elena said. "After everything we've been through, I don't want to risk losing the one person that's helping me get through this." She got up and started to leave. Luckily, she knew the way back from the forest.

Damon was dropping Jeremy off at home. "Well, guess that turned out great for us."

"Whatever."

"Hey, what is your deal?" Damon asked him. "You've been in a mood all day. Does this have anything to do with Anna?"

"I don't want to talk about it." Jeremy told him.

"Look, you're not the only one who's had girl problems, Jeremy." Damon pointed out. "But that's no reason for you to act like a total jerk…"

"She dumped me, okay?!" Jeremy snapped. "She can't stay in town because of John and with Katherine around, you guys need me here. Before she left, she broke up with me. So just back off."

Damon looked at him. He hadn't expected him to react so strongly. He knew Jeremy liked Anna, he didn't know he'd fallen for her. Not knowing what else to say to him, he left.

Upstairs, Elena was in her room when Jeremy came back. "Hey." She said. "How was your trip?"

"We didn't find much about her, but we think this might help." Jeremy handed her the book Damon had given him earlier. "It's her family history. Maybe something in there will help you find out if there's a connection with you two."

"Thanks, Jer." Elena said.

"Are you okay, you look wiped out." Jeremy told her.

"Well, when you're on the run from a werewolf, it tends to wear one out." Elena said.

"Thank goodness you're okay." Jeremy said. "At least after tonight, I've still got you." He left the room. Elena sat down on her bed and opened the book.