Hunting the Hunter (A Supernatural Fanfic/ Imagine)

You are given a mission each month by the agency that you work for. Each month you get a list of names, targets, and they must be taken out before that month ends. But what happens when the newest target is Sam Winchester? And what happens when he finds out secrets about you that even you did not know?
*Kind of an AU because Kevin is still alive & Garth was human*