Chapter 15 (Arya)
Arya is devastated to learn that Harwin is no longer loyal to the Stark family, and his companions are the Brotherhood Without Borders, an outlaw band. Once they were knights loyal to the Starks, but now they have no royal patronage and are wanted men. After traveling some distance, Arya realizes that they are not going to Riverrun to see her family, and instead the outlaws are taking her to Beric Dondarrion, the leader of their Brotherhood. Arya tries to escape, but she is caught and forced to continue on their way to Beric.
Chapter 16 (Samwell)
After the Others destroyed the Fist of the First Men, Samwell and a handful of survivors were forced to flee into the snowfields. Exhausted and feeling defeated, Samwell only wishes to collapse and sleep, or even die. His comrades urge him onward, until they are attacked by one of the Others, here called a “wight.” The cowardly Sam manages to draw his knife, which is made of obsidian, and he stabs the wight. Until now, the undead Others have seemed invincible to all but fire, but when Samwell uses the knife, the obsidian destroys the creature. Samwell and the others continue their torturous march to Craster’s Keep.
Chapter 17 (Tyrion)
Tyrion joins a meeting with his family as they divvy up the spoils of war. Each member of the court receives land and property, but Tyrion is only made the new master of coin. Tyrion doesn't like the post, and he suspects that the Lannister family is destined for financial ruin. Meanwhile, Tywin wants his daughter, Cercei, to marry Willas Tyrell. Cercei vehemently objects to this arrangement, partly because of her ongoing incestuous affair with her twin brother, Jaime. Tywin ignores her objections. Finally, Tywin commands Tyrion to marry Sansa, which startles Tyrion.
Chapter 18 (Catelyn)
Lord Rickard Karstark and his men are brought before Robb, Catelyn, and some of Robb's bannermen. Jaime Lannister had killed two of Karstark's sons in battle and he wanted Jaime executed, but when Catelyn let Jaime free he decided to take revenge by killing two Lannister allies that Robb and his men held as prisoners. The two were just boys. Karstark says it was vengeance, but Robb calls it treason and orders Karstark and his men executed. After failing to hear back from potential allies, Robb seems to lose hope that he can win the wars and keep his kingdom together, and then he ultimately executes Karstark himself. Catelyn has a conversation with Jeyne and tells her that Robb needs an heir.
Chapter 19 (Jaime)
Highwaymen attack Jaime and Brienne on the road, and Ser Cleos is killed. Once Jaime and Brienne deflect the attack, they start to bicker. Jaime grabs hold of a sword, and they duel. Jaime is astonished by Brienne’s fighting abilities, and soon they are wrestling on the ground. A second group of highwaymen surround and threaten them. They are the Brave Companions, also known as the Bloody Mummers, led by Vargo Hoat. After some coarse words, the Brave Companions cut off Jaime’s right hand.
The section gives us another indication of the importance of honor and alliances between families in the world of Westeros. Rickard Karstark is furious that Catelyn released Jaime without consent because he wanted revenge for the deaths of two of his sons. He suggests that getting revenge was integral to his family's honor, and to get that revenge he killed two Lannister allies whom the northerners had captured. Robb, on the other hand, makes it clear that Karstark's behavior was dishonorable as the two prisoners were unarmed and just boys. It's also damaging to Robb to have one of his bannermen undermine his authority by committing such an act without Robb's consent. Though he would prefer on a personal level to let Karstark go, he feels Karstark's behavior damaged his honor, and so he has no choice but to execute Karstark and his accomplices for treason. The move, while preserving Robb's honor, puts Robb in an even more difficult spot than he was already in. Now he will likely lose the support of the rest of the Karstarks, and his support from the Freys is already in jeopardy. Without maintaining these alliances, Robb's entire endeavor is at risk.