You were an FBI Agent on duty. You were guarding a law firm because the head attorney who owned it had gone missing along with some money. He had to come collect the rest at some point. You heard a gunshot and pulled out your own gun to investigate. You stumbled upon a dead security guard and two flashlights in the hallway. You hid behind a wall in wait. When you saw the head of a gun, you kicked it out of the intruder's hand and twisted his arm behind his back while pointing your gun at his partner.
"Drop your weapon immediately," you ordered.
The partner did and you got a good look at the two. The one you were holding was short with green eyes and scruffy hair, while the one you held a gun to was quite tall with brown eyes and longish hair.
"You don't understand what's going on here lady," green eyes spoke.
"I'm FBI Agent Y/L/N. I want your names and an explanation of why you are here," you ordered.
"I'm Sam Winchester and that's my brother, Dean," brown eyes said.
"Well then, Sam and Dean. Why are you here. Are you working for Mr. Sampson?" you asked.
"No. We're here to save people," Dean said.
"How?" you scoffed.
"This is going to sound crazy, but monsters are real. And there's a shapeshifter in here who killed the security guard and will kill you and many more people if we don't stop it," Sam said.
"What do idiot take me for, boys?" You asked in disbelief.
Just then, your perp, Mr. Sampson, entered the room. He had yellow eyes and was growling. You released your hold on Dean and shoved him towards his brother. You aimed your gun at the monster and watched as he got ready to lunge at you.
Sam stepped forward and tackled him. Dean tossed the silver knife at his brother. Sam caught it easily and you watched as he stabbed the monster.
"I believe you," you said, slightly in shock.
"We have to clean this up," Dean sighed.
Sam nodded.
"Go," you told them, "I can take care of this."
"How?" Dean asked.
"I'm FBI," you said.
"We never got your first name," Sam said.
"Y/N," you smiled.
"Well, Y/N, it's been a pleasure," Dean said, leaving
"See you around," Sam added, following his brother.
You finished up your job and thought you'd never see the brothers again. A month later, at a crime scene you were assigned to, you noticed a black 1967 Chevy Impala pull up and the driver honked their horn at you. You walked over and noticed the Winchester brothers in the car.
"Hello again Agent Y/L/N," Sam smiled.
"You guys can call me Y/N," you smiled back.
"How would you like to go hunting with us?" Dean asked.