Who is Cardinal from Mrs. Mike the Story of Katherine Mary Flannigan and what is their importance?

Cardinal is the thief who steals Jonathan's trapped animals for the skins. He is scared away from Grouard by Jonathan when he hears the story of how Jonathan will never stop his revenge. Later, Cardinal is arrested by Mike in a different geographic location and placed in jail for baiting and switching the trapped skins. When Cardinal is stabbed to death in his cell, Jonathan's knife is found at the scene. It is not until Mrs. Marlin attempts to steal the Flannigan's newborn son that Jonathan's innocence is established. Mrs. Marlin admits to killing Cardinal, the father of her aborted baby.