With a single arrow, Katniss kills the boy from District 1, who speared Rue, and takes Rue's hand. Rue makes Katniss promise that she'll win for both of them, and then asks Katniss to sing her a song. Katniss sings a lullaby from her district, and when she's finished, the mockingjays pick up her song. Rue dies and Katniss realizes just how much she hates the Capitol for doing this to Rue, for doing this to all of the tributes. She wants revenge on the Capitol and wonders if there's a way for her to do it. She recalls Peeta's words about showing the Capitol that he's not simply a piece in their Games.
Katniss wreaths Rue's face with flowers and presses the three middle fingers of her left hand against her lips, saying goodbye to Rue. She decides that she will make the Careers pay for Rue's death and gathers her supplies to move on through the woods.
A gift comes to her: an unfamiliar loaf of bread. Katniss understands that it's from District 11 and thanks them. That night, she dreams of Rue singing songs and trying to speak to the mockingjays. When she wakes, she forces herself to keep going and thinks of Peeta and what he'll think of her if he sees how she decorated Rue's body, so that he'll know she understood what he said on the roof that night, about staying true to oneself during the Games. But then she remembers that she promised Rue she'd win for the both of them, so she needs to be the one to survive the Games.
She finds it hard to quit thinking about the boy from District 1 and realizes it's because he was her first true kill, the first person she took action against knowing that her strike would kill him. It bothers her to think of his friends and family and how she's hurt them, how maybe they want revenge upon her. She thinks about Rue in order to block these thoughts out. As she settles down for sleep, a blast of trumpets fills the air, preceding an announcement from Claudius Templesmith. Templesmith announces a change to the rules: This year, two tributes can win, so long as they come from the same district. Katniss calls out Peeta's name before she can stop herself.
This chapter marks an important shift in the novel. With Rue's death, Katniss' hatred toward the Capitol and her desire for revenge against it are at their highest levels. She thinks of all that Gale had to say against the Capitol and how Peeta wanted to make sure he stayed true to himself during the Games, and she understands them both much clearer now than she had before. Katniss is ready to take action against the Capitol and the Careers, and she wants to avenge Rue's death. Her promise to Rue gives her the drive to win, even more so than her promise to Prim. It is also Rue's death that makes Katniss want to shame the Capitol. She does so by adorning Rue's body with flowers, by showing this girl from another district her love, simultaneously telling the Capitol, and everybody watching, that the tributes aren't just pieces in the Games. As she finishes doing this, a mockingjay sings Rue's song. Both the mockingjay's song and Katniss' actions symbolize the Districts' ability to defy the Capitol if only they can work together.
The people of District 11 show their gratitude for Katniss' kindness by sending her a loaf of bread. This is unique in the Games' history; never before has a district sent a gift to a tribute that was not its own. This is exactly the kind of interaction that the Capitol fears. The Capitol doesn't want the districts to unite because then they'll possess more power and stand as a greater threat to the Capitol.
Katniss experiences her first intentional kill in the novel, too, and recalls how Gale said it wouldn't be much different than killing an animal. Katniss decides that in practice it isn't much different, but afterward, the emotions she experiences are very different. She says that she is able to block the boy out of her mind, "At least, for now," which hints at trouble in her future, how she'll have to battle guilt later, and, perhaps, answer to the friends and families of those she killed.
Finally, another major change occurs in the novel and in the Games when Claudius Templesmith announces that, for the first time ever, two tributes can win the Games. This gives Katniss a reason to act on her feelings for Peeta, to find him and save him, while also offering her the opportunity to have him as a hunting partner. She can rely on him in much the same way that she relied on Gale in the woods back in District 12. The rule change also signals that the Capitol and the Gamemakers are experiencing outside pressure, for some reason, to make this alteration. This leads the reader to think that perhaps Katniss and Peeta's partnership, their twinning early in the Games' opening ceremonies, has paid off. Maybe Cinna and Haymitch knew that if the audience could see enough of Katniss and Peeta's affection for one another, that they would want to see both of them live.