A/N: Thank you to everyone who view, reviewed, favorited and followed this story!

I suppose I should have mentioned this last chapter- I am not a Greta fan and I plan on showing her the way she was on the show- pretty selfish, blindly loyal to Klaus and not at all concerned with her family.

I put Thea as a Martin because it worked for the story I wanted to tell, plus I thought it would be interesting to have an OC who isn't automatically affiliated with the Mystic Falls Gang or the Originals (at least at first), but someone who has a separate interest.

I picture Thea as a young Rosario Dawson for some reason. She's beautiful and strong and isn't afraid to say what she thinks. I think she'd make a badass witch.

Thea will be arriving in Mystic Falls during 2x11 (By the Light of the Moon- hence the chapter title). Quick summary- Stefan is stuck in the tomb with Katherine, Jules just arrived in town, looking for Mason and it's Tyler's first time turning.

Anyway, on with the story!

Thea walked down the sunny streets of Austin, smiling as the slight breeze provided a welcome change to the warmer-than-usual late spring weather. She was headed back to the office, after meeting a friend for lunch, her mind already on her upcoming meeting that afternoon.

She was nearly back to her office building when her phone rang. Digging in her purse, she saw her father's phone number flashing on the screen. She contemplated letting it go to voicemail, she really needed to prepare for this meeting, but Jonas rarely called, so it could be important.

"Hello?" she answered, stepping into the air-conditioned building.

"I think I found her," came her father's voice.

Thea took a sharp breath inward, mind reeling.

It had been two years since she'd watched Greta walk away on that sidewalk. She'd heard from Greta a few times after she'd left, then the calls stopped. It had been more than a year and a half since they'd had any contact. Emails weren't returned and Greta's phone had been disconnected.

At first, Thea was sure Greta was just busy. But as time wore on, she began to fear something had happened to Greta. Had Klaus done something to her? Had she been killed by an enemy of Klaus' (he had no shortage)? Or worst of all, had she willingly forsaken her family?

Jonas had begun a crusade to find his lost daughter, devoting all his time and energy to the cause.

Thea and Jonas' relationship became strained, as Jonas blamed Thea for letting Greta go. They rarely talked. Luka, Thea's younger brother, had been the one who kept Thea mostly informed on their progress towards finding Greta.

"You found her?" gasped Thea. "Where? Where is she?"

"I don't know where she is," Jonas admitted. "But Elijah knows where Klaus is going to be."

Thea frowned slightly at the mention of Elijah's name. Jonas and Luka had been working with Elijah for the past few months. They had met during their mutual search for Klaus.

Thea had never met Elijah, but she couldn't help be distrustful. He was an Original, after all, just like Klaus, and seemed reluctant to share his reasoning for wanting Klaus dead, just that they had a 'falling out'. Jonas, desperate to find Greta, said he didn't care who they got help from, as long as she was found.

"Where is Klaus going to be?" asked Thea.

"A small town in Virginia," said Jonas. "It's called Mystic Falls. We're on our way there now."

"Okay," said Thea. "When is Klaus going to be there?"

"We're not sure," said Jonas. "Elijah thinks he's going there to break the curse."

"Did Elijah find a doppelganger?" gasped Thea.

This was bad. Really bad. They couldn't let Klaus break the curse.

"Yes," said Jonas. "Her name is Elena Gilbert."

"When is Klaus coming? The next full moon is in five days," said Thea. "Think it'll be that soon?"

"Doubtful," said Jonas. "Elijah says Klaus won't show himself until he's recovered the moonstone."

Thea rolled her eyes, remembering how paranoid Klaus was. It was why he'd eluded his enemies for so long.

"Do you know where it is?" asked Thea.

"No," said Jonas. "But Elijah is working on it."

"Okay," said Thea, still not trusting this 'Elijah' person. "I'll be there as soon as I can, I just need to let my boss know..."

Jonas cut her off.

"You don't need to come, Thea," said Jonas. "Luka and I can handle it."

"What?" frowned Thea. "Of course I'm coming. Why did you call if you don't want me to come?"

"Luka insisted," said Jonas, clearly not happy about it.

"Look, Dad," said Thea, trying to keep her voice even. "I know we haven't always seen eye to eye, especially since Mom left..."

"Please don't bring your mother into this," said Jonas.

"But stopping Klaus and getting Greta back are what matters," continued Thea. "I'll let you know when I'm coming."

Jonas sighed. "Fine. I'll text you the address of the apartment we're renting."

Thea hung up the phone and took a deep breath. She'd both hoped for and dreaded this day. She wanted to protect her sister, but did not want to face Klaus. No matter what happened, she had to stop him from breaking the curse.

o – o – o

Thea knocked on the apartment that Jonas was renting. After a minute, the door opened and she saw her father standing there.

"Hey, Dad," said Thea.

"Thea," he responded, trying for a smile.

They had an awkward hug and she walked into the apartment, remembering the last time she'd seen her father. It was at Thea's college graduation, a few months after Greta had left with Klaus. Luka and Jonas had traveled from Louisiana to The University of Texas-Austin, to see Thea graduate.

They had managed to maintain their civility and Jonas was in a good mood, on the campus of his alma mater (which is why both Thea and Greta had chosen the school, as well as its resources and unofficial sub-culture of witches), until the night of Thea's graduation dinner.

Austin, Almost two years ago

"This place is great, Thea," said Luka, digging into his plate. "I've never had Ethiopian food before."

"It's one of my favorites," smiled Thea. "It's just down the street from my new job."

"You got a job?" asked Jonas, surprised.

Thea smiled. "Yeah. I told you one of the local coven leaders works in Marketing. She gave me a job. I'm lucky, especially in this economy."

Jonas' expression was not one of joy.

"I thought you'd be happy for me," frowned Thea.

"I'm glad you found a job, honey," said Jonas. "But I was hoping you would come with us."

"With you?" asked Thea, confused. "Where are you going?"

Jonas put down his fork and sighed. Luka all of a sudden looked nervous and was intensely studying his plate.

"I've closed my practice," said Jonas. "I'm going to look for your sister. There are rumors that Klaus is in South America."

"South America?" Thea repeated. "What about Luka? He's a sophomore in high school."

"I'll teach him," said Jonas. "We both can."

"Dad, this is crazy," said Thea. "It's only been a month since we've heard from her, Greta's probably just busy."

"Do you really believe that?" challenged Jonas.

Thea was silent. No, she didn't.

Jonas' expression hardened. "Klaus has done something to her. Or one of his enemies. I still can't believe you let her..."

"Let her?" hissed Thea. "You've got to be kidding me! She was 19, Dad. An adult. What was I supposed to do? Chain her to her dorm room?"

"You should have stopped her from working with him in the first place!" exclaimed Jonas. "She's your little sister and you were supposed to protect her."

Tears formed in Thea's eyes. That's what it all came down to. Ever since her mom left, she'd been tasked with taking care of her younger siblings, when Jonas would work long hours at his medical practice, or go off to indulge in his obsession- the collection of grimoires.

It had been an ongoing point of contention whenever Thea's own interests had conflicted with her family responsibilities. The past four years of being away at college had been liberating.

"Greta made her choice," said Thea, trying to blink back tears. "Even if you find her, how can be sure she'll want to come back?"

"Greta would never willingly serve him," said Jonas. "He manipulated her."

"Of course he did," said Thea, rolling her eyes. "That's what Klaus does. I argued with her endlessly about this and couldn't change her mind. What makes you think you can?"

"She'll listen to her father," said Jonas.

Thea sighed. "I hope you're right. But I can't go with you. My life is here."

Their relationship had been strained after that and she hadn't seen her father since.

"I'm surprised you actually came," said Jonas.

"I said I would," frowned Thea.

"You seemed determined to stay in Austin the last time we saw each other."

"Things have changed since my graduation," said Thea. "We haven't heard from Greta in almost two years. I don't know if she's dead or a prisoner or..."

Thea trailed off, not wanting to think about the alternative- that Greta had cut her family off willingly.

"What matters is getting her back," said Jonas. "Elijah has a plan. To kill Klaus."

"Kill Klaus?" frowned Thea. "You can't kill an Original vampire. And what good would that do anyway?"

"If Klaus is dead, Greta will have no choice but to come back to her family," said Jonas.

Thea raised an eyebrow. "And you don't think Greta will be a little upset you killed him?"

"She'll understand," said Jonas. "Greta was always stubborn, but she was a sweet kid. Klaus is manipulating her."

Thea frowned, but didn't comment. She loved her sister, but while Greta was definitely stubborn, she wasn't particularly sweet. She had always been a little selfish and it had only gotten worse as Greta had gotten older.

Greta as a teenager had been insufferable; Jonas just hadn't noticed much as he was gone a lot, leaving Thea to deal with Greta's rebellious ways. Thea suddenly wished she hadn't covered so much for Greta when they were younger.

"Let's just find her," said Thea. "So when do I get to meet the famous Elijah?"

"He comes when he needs something," said Jonas. "And to give us updates."

"So he's running the show, huh? Taking orders from a vampire?"

"We have a common goal, Thea," said Jonas. "If you came here to do anything besides get Greta back, it's best you leave."

"Why don't you just tell me the plan?" said Thea, tightly.

o – o – o

"That's the plan?" exclaimed Thea, a few minutes later. "Sacrifice three people, then kill Klaus by channeling the power of witch massacre site you can't even find!"

"Elijah said he has a way to save the doppelganger," said Jonas, defensively. "He's personally trying to find the witch site."

"That still leaves a vampire and a werewolf to be killed," said Thea, horrified. "Please tell me there is a Plan B."

"No, Thea," said Jonas, heatedly. "This is plan. Klaus has to die, so Greta can be free."

"Now I know why you didn't want to call me," Thea practically shouted. "This is crazy! There has be another way to stop Klaus, without killing people!"

Jonas sighed. "Elijah says it's impossible."

Thea clenched her jaw. "Where is Elijah?"

"He's out looking for the witch massacre site," answered Jonas.

Thea sighed. "If that place is as powerful as you claim, there's got to be a way to use it to put down Klaus. Hold him down long enough trap him. I think I read a spell somewhere that will immobilize a vampire for a few hours..."

"Klaus is an Original," said Jonas. "There isn't another way."

"Dad, this isn't you," said Thea, almost pleading. "You're a doctor. 'Do no harm.' You aren't this person."

Jonas sighed and closed his eyes, looking older and wearier than Thea had ever seen him.

"You have no idea what I've been through," he said, clearly trying to control his emotions. "These past two years, not knowing if my little girl was alive. If she was hurt or scared. I've done things, Thea. Things I never thought I..."

Jonas trailed off, rubbing his hand on his head in frustration.

"I'm sorry," said Thea, sighing. "I should have come with you. I didn't think... You shouldn't have had to go through this alone."

Thea moved closer and wrapped her arms around her father, trying to comfort him.

They talked for a while longer, steering clear of all things Klaus/Greta/Elijah-related, until Thea announced she was hungry.

"It's fine," said Thea, waving Jonas off. "I can go get a bite to eat by myself."

o – o – o

If the menu was any indication, the Mystic Grill was a small town diner with nicer finishings. Still, Thea was famished and the waitress was polite as she took Thea's order.

She was just coming out of the bathroom, ready to go back to her dad's apartment when she noticed a guy with light brown hair stealthily putting something into a blonde woman's drink at the bar, while another guy in a leather jacket distracted the woman.

"What the hell?" she muttered, walking over to the trio.

As she got closer, she realized the guy in the leather jacket was a vampire. The perks of being a witch, though she wasn't sure she'd ever seen a vampire use roofies. How modern.

"Thank you for the drink," said the blonde woman, as Thea walked up.

"Don't drink that!" Thea exclaimed, grabbing the glass out of the woman's hands. "His friend put something in it."

The vampire turned around and grabbed Thea by the shoulders.

"You must be mistaken," he said, softly.

Thea clenched her jaw at the attempted compulsion.

"I was just mixing it," said the other guy, slurring his words. "See?" He took a sip from drugged drink. "Nothing in there but the Grill's finest."

Thea frowned, she knew what she'd seen. If he hadn't put some type of drug in the drink, what had gone in there? What was going on? Jonas had warned here that this town was a hotspot for supernatural activity and that nothing was what it seemed. He said it was a miniature New Orleans.

Of course, Jonas had also told her that the vampires in this town were protecting the doppelganger, Elena, so they weren't to be harmed.

"I'm Alaric, pretty lady," said the guy with light brown hair. "What's your name?"

"Thea," she said, cautiously.

"Buy you a drink?" he asked, still slurring a bit.

Behind her, the blonde woman and the vampire had resumed their conversation, though the blonde hadn't touched the drink.

Whether they were protecting Elena or not, Thea decided she was going to find out what exactly Alaric put in the woman's drink. She breathed in, calling forth her magic. She raised her hand and immobilized Alaric. As a human, with human-level strength, it wasn't much of a challenge.

Alaric's eyes widened as he realized he couldn't move, or speak. Thea dug in his pocket and found the small packet.

Thea frowned when she recognized the herb immediately. It was wolfsbane. Thea released Alaric and dragged him to the far side of the restaurant, away from the bar and the vampire and the blonde.

"You're a witch," muttered Alaric, dropping the drunk act.

"And you're a human that just added wolfsbane to that woman's drink," said Thea, quietly. "Why?"

Alaric looked at her appraisingly. "Who are you?"

"I told you. I'm Thea... Martin. You might know my father?"

"You're working with Elijah," said Alaric, eyes narrowed.

"I'm not working with him," Thea said, with more venom in her voice then she intended. "I've never even met him."

"Then why are you in Mystic Falls?" asked Alaric, still looking at her suspiciously.

Thea looked at him and decided to tell him a half-truth. Jonas had warned her about telling anyone about Greta. She thought it was silly, but didn't want to betray her father's trust.

"Because Klaus is going to be here," said Thea. "And he took something from my family. Something I want back."

"What did he take?" asked Alaric, now looking concerned.

Thea shook her head. "It doesn't matter. We just need to find him and stop him. We can't let him break the curse. It's too dangerous."

Alaric nodded. "Well at least we agree on that."

"Your turn," said Thea. "What's with the wolfsbane? And who's the vampire?"

"How do you know he's a vampire?"

Thea smirked. "Witch trick. So...? Come on, I showed you mine."

Alaric looked hard at her one more time and sighed. "His name is Damon. We're trying to find out if that woman is a werewolf."

"Why?"

"We think she's friends with another werewolf who came into town about a month ago."

"And where's this werewolf now?" asked Thea.

At Alaric's hesitant face, Thea shook her head. "Let me guess, your vampire friend killed him?"

Alaric tilted his head in affirmation.

"Vampires and werewolves," said Thea, shaking her head. "You should tell your friend Damon he might want to lay off. At least for the night. It's a full moon. You do know a werewolf bite is fatal to a vampire?"

Alaric nodded. "Damon doesn't like to be told what to do."

Then Alaric looked over Thea's shoulder, concerned. Thea turned around and saw that Damon and the blonde woman were having a heated argument.

Alaric got up and made his way over to them.

"Damon, how about that second round?" asked Alaric, trying to diffuse the tension.

"I think we're done, Ric," said Damon. He turned to the blonde woman. "You think I'm afraid of you?"

"No, I don't," said the blonde woman. "That's your vampire arrogance... You should be. I sniffed you out the moment you entered this bar. Along with your pathetic wolfsbane."

The woman sent a withering look at Alaric.

"See, I've been at this a long time," the woman continued. "And any other night of the month, the situation would be reversed. But tonight, is not the night to pick a fight with me." She angrily got up. "You've been marked."

Thea's eyes widened. That didn't sound good. She hadn't had many dealings with werewolves, they were pretty rare and nomadic, but she knew they were fiercely loyal to their own. If this woman had figured out Damon had killed her friend...

The woman walked away. Damon moved to follow, but Alaric stopped him.

"We're in public, man," said Alaric, putting a hand on Damon's arm.

Damon shook off Alaric's arm and turned to Thea.

"Thanks for that," he said, angrily. "Your little interruption tipped her off."

Thea crossed her arms. "I thought you were trying to date rape her. What was I supposed to do?"

"Do I look like someone that needs to drug a woman to sleep with her?" asked Damon, moving towards the door.

"If I say yes, is he going to try and bite me?" asked Thea.

"He might try and bite you anyway," said Alaric, shaking his head. "I should go after him."

Thea nodded. "Tell him to stay inside. Werewolves prefer the outdoors."

"It was nice to meet you, Thea," said Alaric, smiling. "I hope you find what you're looking for."

Then he walked out of the Grill.

o – o – o

When Thea arrived back at her father's apartment, Jonas was reading.

"Where's Luka?" asked Thea, shrugging off her coat.

She hadn't had a chance to see her little brother yet.

"Sleeping," said Jonas. "It was a long day."

"What happened?" asked Thea. "Is he okay?"

Jonas nodded and told her that Luka had spent most of the day with Bonnie Bennett, lying to her about de-spelling the moonstone, then had worked with Jonas to lower the seal on the tomb to let out Elena's boyfriend Stefan Salvatore, based on the deal that Elena had made with Elijah.

"Well they all know you're working for him now," said Thea, shaking her head. "I ran into a few of their gang at the Grill. Alaric and the vampire Damon. I'm guessing that's Stefan's brother."

"What did you tell them?" asked Jonas, concerned.

"The truth," answered Thea, shrugging. "That Klaus took something from our family. That I want to stop the sacrifice."

"Thea..." Jonas trailed off, annoyed.

"Don't 'Thea' me," she said. "I..."

She trailed off when she saw a white stone laying on the table beside Jonas.

"Is that..."

"The moonstone," confirmed Jonas. "The key to breaking the curse."

Thea rolled her eyes. "One of the keys." She sighed. "I'm tired, I'm going to bed."

"I made up the daybed in the den," said Jonas.

Thea smiled and wished him goodnight. She waited for another few hours, after Jonas had gone to bed before sneaking out to the living room.

After a few minutes of searching, she managed to find where Jonas was keeping the moonstone. She picked it up and closed her eyes.

"I'm sorry, Dad," she whispered to herself.

Then she took the moonstone and went out the door. When she returned an hour later, sans moonstone, she crawled into bed, hoping her father would forgive her one day.

A/N: I hope it makes sense how Thea views Elijah and Jonas' plan at the moment. To be fair, it is not a nice plan, even when you consider the elixir. Next chapter, Elijah will enter- three guesses at what he'll be looking for?

As you've probably already guessed, I'm going to be making some changes to canon- Let me know what you think so far!