You met John Winchester in Delaware, you helped him since you also were an hunter. Though you never worked alone, you were too young to do so. So as he knew you had potential and his sons, Sam and Dean, might always need some extra help, he sent you to partner with them to hunt.

So when they got to Pennsylvania to hunt a poltergeist in an abandoned building, you detected their position and you went to knock on their motel's door. at first, they were alarmed. They didn't know who you were.

It was Sam with a suspicious gaze that opened the door.

“...Yes? How can we help you?”