In Game of Thrones season 1, episode 9 "Baelor," the Lords of the North, describe Lord Walder Frey of the Twins as an untrustworthy man. Since Lord Eddard Stark of Winterfell rots in a dungeon below the Red Keep, his heir, Robb Stark summons the Northern bannermen. He marches South with his host, and as they approach the Trident River, they realize they need House Frey's permission to cross the only viable bridge over the Green Fork. Catelyn Stark suspects the Freys of sending word of Robb's movement to the Lannisters, while Robb says since the Lord of the Crossing is his maternal grandfather, Lord Hoster Tully's bannerman, they should expect his support. Greatjon Umber reminds the Young Wolf: