Robb's smile was hidden behind Arya as he gave her another squeeze, now realizing this anger was her lashing out from the pain of everything that's happened to them these last few months. It hurt him to see her like this, to see her innocence lost and talking of foolish things such as murdering the Lannister king.

What have they done to you, Arya? And of Sansa? He thought to himself. If Arya was in this sort of state, he hated to see how Sansa was, given they both secretly knew she was the softer of the sisters.

"That day will come. This I swear to the gods." Perhaps he shouldn't be making false promises, but knowing it was his duty to avenge his father, he felt confident enough to know what his next role would be.