After winning the 74th Hunger Games in the previous novel, Katniss Everdeen and Peeta Mellark return home to District 12, the poorest sector in the country of Panem. But on the day that Katniss and Peeta are to start a "Victory Tour" of the country, President Snow visits unexpectedly and tells Katniss that he is angry with her for breaking the rules at the end of the last Hunger Games, which permitted both Peeta and Katniss to win. Snow tells Katniss that when she defied the Capitol, she inspired rebellion in the districts.
The first stop on the Victory Tour is District 11, the home of Katniss' deceased friend and ally in the Hunger Games, Rue. During the ceremony, Katniss delivers a speech thanking the people of District 11 for their participants in the Games. When she finishes, an old man whistles the tune that Katniss used in the arena to tell Rue that she was safe. The song acts as a signal and everyone salutes Katniss, using the same gesture that she used to say farewell to Rue. To the horror of Katniss, the old man and two others are executed.
Katniss and Peeta travel to the rest of the twelve districts and the Capitol. Hoping to placate the growing rebellion and settle the dispute between Katniss and President Snow, Peeta proposes to Katniss during an interview. Despite this, Katniss learns that their attempt to avert revolt in the districts has failed.
Shortly after returning to District 12, Katniss discovers on the mayor's television that District 8 has had an uprising, and she fears that what she has done to placate the crowds is not enough as there may be uprisings in other districts as well. She then meets two runaways from District 8, Bonnie and Twill. They explain their theory which contradicts what the other districts have been led to believe: District 13 was not completely wiped out by the Capitol, and that its residents survive in underground shelters.
Later, it is announced that, for the 75th Hunger Games, twenty-four victors from previous years will be forced to compete once again. This is the third occurrence of the "Quarter Quell": an event that occurs every 25th year of the Games and allows the Capitol to introduce a twist. Knowing that she and Peeta will both be competing in the Games a second time, Katniss decides that she will devote herself to ensuring that Peeta becomes the Quarter Quell's victor and convinces her mentor to try and help her. Likewise, Peeta is devoted to protecting her, but both Katniss and her mentor are determined that only Peeta reaches back home safely.
During the Games, set in a jungle with a saltwater lake, Katniss and Peeta join up with two other previous victors: Finnick Odair, a 24-year-old man who survived the Games at the age of 14, and Mags, Finnick's 80-year-old mentor, both from District 4. The party encounters poisonous fog in which Peeta comes into contact with the gas and cannot walk. Mags sacrifices herself in order to save Peeta and dies in the poisonous fog. After Mags's death, Katniss, Peeta and Finnick join forces with Johanna Mason, a sarcastic and often cruel victor from District 7, and Beetee and Wiress, an older couple from District 3 who are said to be "exceptionally smart". Wiress soon proves her genius by revealing to Katniss that the arena is arranged like a clock, with all of the arena's disasters occurring on a timed chart. After Wiress is killed in a battle with the Careers, Katniss learns of Beetee's plan to harness lightning in order to electrocute Brutus and Enobaria, the two remaining Careers Tributes from District 2. In the final chapters, Katniss instead directs the lightning at the force field that contains the arena, thereby destroying the arena and resulting in her temporary paralysis.
When Katniss wakes up, she is being transported to District 13, joined by Finnick, Beetee, and her mentor, Haymitch Abernathy. She learns that Peeta, Enobaria, and Johanna have been captured by the Capitol, and is informed that there had been a plan among half of the contestants to break out of the arena— Beetee had been attempting to destroy the force field in the same way that she did. The book ends when Katniss' best friend, Gale, comes to visit her and informs her that, though he got her family out in time, District 12 has been destroyed.