<P> At camp, Catelyn counsels her son Robb, the King in the North, about his planned alliance with Lord Walder Frey and his planned assault on Casterly Rock, the homeland of the Lannisters . The Stark host soon arrives at the Twins, castle homeland of the Freys, where they are given bread and salt, a symbol of the "guest right": a guarantee of safety when under another lord's roof . Robb makes an apology to both the sarcastic Walder Frey and his daughters . Walder accepts the apology but insists on inspecting Talisa, the woman for whom Robb broke his vow . Nearby, Arya, though still a captive of Sandor Clegane, journeys to the Twins to reunite with her mother and brother . When they come upon a trader and his cart, Clegane knocks him out and moves to kill him, but Arya manages to dissuade him, and he instead steals the cart of food . </P> <P> At night, Walder walks his daughter Roslin down the aisle to her future husband Edmure Tully, who is pleasantly surprised by her beauty . They are married shortly after, and the celebration begins . At the feast, Walder calls for the bedding ceremony, and the couple are taken to their chamber . After they leave, Lothar Frey closes the banquet hall doors, and the Frey bards begin playing "The Rains of Castamere", a Lannister cautionary song, both of which arouse Catelyn's suspicions . Using the food cart as their reason for being at the Twins, the Hound and Arya arrive at the wedding . They are turned away at the gates, but Arya sneaks in . </P> <P> Catelyn notices Roose Bolton wearing chainmail under his robes which confirms Catelyn's suspicions that they have been betrayed . Just as Walder signals his men to attack the Starks' men, Catelyn tries to warn Robb, but before he can react, Lothar repeatedly stabs the pregnant Talisa in the stomach, killing her and her unborn child . As he tries to draw his sword, Robb is shot by crossbows, and the massacre of his bannermen begins . Arya, having snuck past the gate, witnesses Frey men kill Stark soldiers and Robb's direwolf, Grey Wind . She is saved by the Hound, who knocks her unconscious and carries her out of the castle . Catelyn, although wounded by a crossbow bolt, holds Walder's young wife, Joyeuse, hostage with a knife and demands that Robb be allowed to leave . Walder refuses, and Roose Bolton stabs Robb in the heart, delivering Jaime's message from Harrenhal, "The Lannisters send their regards ." Catelyn screams and kills Joyeuse in retaliation, before Frey's son Black Walder cuts Catelyn's throat . </P> <P> "The Rains of Castamere" was written by executive producers David Benioff and D.B. Weiss, based on George R.R. Martin's original work from his novel A Storm of Swords . The episode adapts content from chapters 41 to 43 and 50 to 53 (Bran III, Jon V, Daenerys IV, Catelyn VI, Arya X, Catelyn VII, and Arya XI). </P>

Who killed the starks at the red wedding