Samuel Campbell is the father of Mary Winchester, Sam and Dean's mother. He appears first in the Season 4 episode In The Beginning when Dean traveled back in time with the aid of Castiel. Dean met Samuel after spying on Mary at a diner and Mary kicked his ass. Samuel was investigating a sighting of the yellow-eyed demon, Azazel, at a farm house. Azazel later possessed Samuel and stabbed him fatally before vacating the body. Samuel has returned beginning in the Season 6 episode Exile on Main Street without an explanation of his resurrection beyond the rather cryptic assumption that whatever force elevated Sam from Hell dragged Samuel back from Heaven. Samuel introduced first Sam, and eventually Dean, to several cousins, other Campbells who are in the Hunting life.