Bilbo said "Thorin, it wouldn't hurt to rest the night somewhere more secure then out there...this place we can keep better watch and I can repay my debt to Lady Serena" Serena turned, confused. Bilbo went on and said "she saved my life, and I feel I can repay her by being a witness to these creatures she hunts." Gandalf smiled and said "Thorin...you have a debt to her and Master Bane as well..."