Summary: Natsu Dragneel is a Detective for Magnolia PD working on a case to bring down the infamous Sabertooth Gang. When their only undercover is found dead, they have to look towards an unlikely person in the hopes that she could help to bring down her fiance and her father. Will she help the PD? Or will she turn against them and tell her father and fiance about their investigation? Will she become the agent that Natsu needs or a double agent who gives off misleading information?

Heiress Undercover

Chapter 1

The news no one wants to hear

Strolling into headquarters, Natsu's pink hair swayed softly with each step. A smile adorned his handsome features and he flashed a toothy grin at all the coworkers that he passed. Each shot him a quick greeting, him returning most with a wave or a simple "hey," as he walked. Reaching his desk, he pulled his gun and holster from his side and placed it into the bottom drawer before taking a seat and staring at the large pile of folders sitting on top of his desk.

His charcoal eyes closed for a moment as a sigh passed through his lips. If there was anything he hated about his job, it was the paperwork! Being a detective, he loved the thrill of hunting down the criminals. The stakeouts, the chase, and finally, the capture. It was always a rush when he caught the one behind whatever it was they were doing. Leaning forward, he pressed the power button on his computer as he heard the quiet hum of it coming to life. His screen lit up, showing the Windows logo and then asking him for his log in information.

Just as his fingers moved to the keyboard, a voice called out behind him making him pause in his actions and turn around. His dark eyes landed upon the deep blue ones of none other than Mirajane Strauss. She had, at one point, been one of the best detectives known to Magnolia PD. But that has long since changed. She was no longer willing to work in the field and now remained behind the desk as a receptionist. "Natsu, the captain would like to see you." She stated, her voice as sweet as it always was.

With a sigh, Natsu nodded and thanked Mira for relaying the message before standing up and making his way towards the back where the captains office was. In the corner of his eye, he could see his long time best friend and rival smirking at him. The dark haired man was leaning back in his chair, his booted feet propped up on his desk with his hands behind his head. "What did you do this time, flame brain?" Gray Fullbuster questioned. Natsu shot him a look, silently relaying for him to back off for he himself wasn't even sure.

It was never a good thing when the captain asked to see you. Normally she would just send Mira with whatever instructions she had. The only time she saw you personally was when you fucked up. Running a hand through his pink locks, Natsu stopped just outside the all white door that held a plaque on the side that read "Captain Erza Scarlet." Tapping three times on the door, he heard the okay on the other side of the door for him to enter.

Charcoal met brown as he locked eyes with his boss, her gaze stern and her expression showed that she wasn't very happy. Then again, she never really was. "Dragneel, thank you for coming in so quickly. Please take a seat, we need to talk." Natsu eyed the red head for a moment, this was definitely not good. Normally she would just start right off with scolding him for whatever he had done wrong, so what was so bad that she wanted him to sit down?

Erza grabbed the water that was sitting on her large oak desk and took out two small pills to deal with the constant headaches she always seemed to have. Shoving the pills into her mouth, she quickly swallowed them with a long gulp of the water before closing the lid and turning her attention back to the pinkette who finally took a seat. "Natsu, we have a problem."

"I figured as much, you don't usually make me come all the way to your office just to give me an assignment or something." The pinkette responded. Erza narrowed her beautiful brown eyes at the sarcasm that laced his words. Clearing her throat, she continued as if he hadn't said anything which only served to worry Natsu even further. "Your informant in the Sabertooth case, Yukino Aguria," She paused as she waited for Natsu's acknowledgment. When he nodded, she took a breath and continued. "She's been found dead."

Natsu's dark eyes widened, shock immediately taking place over the cautious look he had been wearing a moment ago. "What?" He questioned, hoping that he had heard Erza wrong. Erza sighed, she knew that this would be difficult for Natsu to hear. Not only did he personally ask Yukino for help, but he had promised to get her out of this situation once everything was finished. Natsu had grown to like the white haired girl, even if only as a friend.

"Yes, unfortunately it's true. It seems her cover was blown. They found out that she was working for the police, even though they don't actually know what branch but once they even hear a rumor of such things, you're done for." Natsu knew this all too well. Yukino may have been the first informant he had in this case, but he had seen what happened to anyone who betrayed the Sabertooth gang. It never ended well.

Natsu leaned forward, placing his forehead in his hand as his elbow leaned against his knee. How could this have happened? Last he checked, they had no idea what Yukino was doing. It didn't seem as if they suspected anything! "H-how?" Natsu managed to choke out. He just couldn't figure out how they knew! Another sigh came from the red head as she leaned back in her chair and began to massage her temples. All this stress was going to give her wrinkles.

"I'm not sure, Natsu. No one is. Everyone was certain that she hadn't been discovered. There wasn't a single sign that they had suspected her." She explained. Everything that had anything to do with this case seemed to go wrong. As if it were cursed or something. "So, now we have to figure out what we're going to do next." Erza stood up, turning her back to him as she gazed out the floor to ceiling windows.

"Any ideas?" Natsu asked, he himself had no clue where to go from here. She was his only way inside the gang, his only way of gathering information since Sabertooth kept themselves way too guarded for anyone of their own undercover's to get in. Erza continued gazing out the window, her lips stretched into a thin line as she thought hard on this situation.

"I fear the only thing we can do is go to her." Once more, Natsu found his eyes widening. He stood up quickly, his mind racing. How could they ever manage to turn her against her own fiance? "How am I supposed to do that?" Natsu asked in exasperation. Were they really getting that desperate to take such a risk? This could blow their entire operation to bits. Completely destroy months of hard work in a matter of minutes!

"Look, we need someone higher up on the food chain. Someone close to Sting. Yukino was a great pick, but she's no where near the other. If this goes well, we'll have an informant who is constantly by Stings side and the one he would least suspect. What's even better is that she's not only close to Sting, but Jude as well. And if she truly doesn't know about what they are up to, then she would more than likely help us." Erza elaborated.

"But what if she does know?" Natsu questioned. There were just too many if's when it came to this plan. What if she does know? What if she's involved? And if she doesn't, how do they know she won't just run for the hills? What if she tips off Sting to what they are doing? Or gives them false and misleading information? "We will just have to deal with that when we get to it. But I'm fairly certain that she doesn't know."

"But this is her own father and her fiance we're talking about! How can you expect her to betray them?" Erza turned to face him this time, brown eyes gazing at him. The wisdom and experience that Erza had was clearly shown within her deep brown eyes. "I don't expect anything. We can only hope that she is willing to help us."

Natsu left Erza's office not too long after that, a scowl present on his lips. He had no clue on how he was going to manage this, but it seemed that Erza had complete faith in him, which was definitely something new to him. She usually expected him to fuck something up, he wasn't sure what to make of this change. "Hey flametard, what did the captain say this time? Did you destroy another building while trying to apprehend one lousy criminal?"

Natsu's gaze shifted to his dark haired rival, his eyes narrowing dangerously. "Shut the fuck up, prick! You have no idea what just happened!" The serious tone that Natsu used had surprised Gray. His dark brow furrowing in confusion. He stood up, having been in the same position as when Natsu first walked passed him earlier. He closed the short distance that was between him and Natsu, placing his hands in his pockets.

"What's up? What happened in there?" Gray asked, rather worried about what had gotten Natsu in such a fowl mood. Normally, Erza scolding him would just scare him a bit but he would still in the end laugh a bit about it. No, this was something completely different. Natsu sighed, shooting his rival a quick glance before he explained all that Erza had said and at the end, Gray stood there, staring at him with his mouth hanging open.

"Are you serious? She wants us to try and pull the Heartfilia heir into this?" Gray seemed just as shocked as Natsu was when he was first told. When Natsu nodded in response, Gray closed his mouth, trying to swallow this new bit of information. "I can't believe Yukino's gone." Gray practically whispered. Everyone here at the station was getting used to having her around. She was always friendly and kind, it just seemed that she had gotten involved with the wrong people at a young age and was never able to get out.

"Tell me about it." Natsu sighed once more before heading back over to his computer and sitting down. He had a lot of thinking to do and had no idea where to start. How would he ever manage to get close to the girl? She was always surrounded by friends and gang members, even if she didn't know who they were. Then again, maybe she did know. It was hard to tell. She never gave off the impression of someone who would be willing to do the things that her father and fiance have done, but maybe she knew about it but chose to ignore it? Only time will tell and Natsu had a lot to do in the mean time.

A/N: Hello again! I'm back once more and would love to know what you think of this. This has been sitting in my documents for about maybe five months now and I actually really like this one. I read a lot of James Patterson books and this is right up my alley so please, let me know what you think! Thanks so much!