He has never stopped searching for her, believing that finding her would bring him the peace he needs to move on. However, Holder could not have anticipated that he would be faced with even greater pain the moment they reconnected. In Losing Hope, Holder reveals the way in which the events of Sky's youth affected him and his family, leading him to seek his own redemption in the act of saving her.
But it is only in loving Sky that he can finally begin to heal himself.