Mario Guerrera was the latest addition to Dr. Joshua Leeds' cosmetic surgery team, which felt, to him, like a piece of great good fortune, until there was "A Death in the Family". Dr. Leeds' murder, Beckett and Castle discover, was due to his work on the side for the D.O.J., providing new faces for those in Witness Protection whom the Department wanted to give a fresh start. One such was Jimmy Moran, formerly of the Spolano crime family, whose defection did not go down well. In fact, such was the Spolanos' concern, they sent one of their top hitmen to locate and eradicate "The Rat".