So, I figured it could use some "previously on"s.
The full nine chapters and prologue are at AO3.
Just to keep it easier
The districts have opted to go to war in what will later be called "The Dark Days." Dale Everdeen, a "Ridgie" (original inhabitant) of District Twelve, who married a merchant girl, is dubious about the prospect, but wants a better world for his little son, Effrim. Old Pappy Angus Abernathy, an octagenarian who saw combat as a young man, thinks the firebrands are nuts, and on this, he isn't far off... along with the agitating against the Capitol, Thirteen's people are also agitating against the merchants, which causes bad blood everywhere.
Seven years after the declaration of hostilities, Dale is missing in action and Effrim is dealing with Thirteen's de facto occupation of Twelve, with "Teachers" demanding perfect compliance in word and deed with their doctrines. He gets wind of the fact that they suspect his father of desertion and, worse, spreading dissent in the ranks, and finds out that they mean to question him about it... and his experience tells him that this questioning is not apt to be particularly civil. He hides at Pappy Angus's, where a girl two years ahead of him, Duronda, is able to give warning and tell him that his friend, Misty, is waiting in the woods.
Misty not only has brought provisions, but announces that she means to accompany him. They get a slow start, and the next morning, Duronda herself catches up to them, berates them for their slowness, and promptly joins in. The three of them make their way through the ruins of Appalachia, following first a river, then the ruins of a highway, to the ruins of Charleston, West Virginia.
There, they run across a band of out-district raiders, led by a rich Capitolite murderer named Trajan and his District Two sidekick, Verus. They are captured and put in with several other children who are due to be sold. The girls are "prettied up" and Effrim is introduced to the horrors of life as a raider, scavenging battlefields and robbing military camps while Trajan murders his way in.
They decide to make an escape while the armies are nearby, so they'll have somewhere to escape to. Effrim, who's been entertaining the camp at night with his singing, distracts them while the other children arrange a sudden black-out. Effrim calls on the jabberjays he's befriended and creates a cacophonous round of "The Hanging Tree," and under cover of the confusion, they escape.
Near the river, they meet a District One soldier who heard "the old school song" being carried by the jabberjays and realized that someone was in trouble. She takes them to the rebel camp, where they're interviewed by a soldier who wants to send them back home. They don't give their information, though the other kids do, and the rebels get them back to their people, even the little Capitol girl, Juliana. The boy who had been with the raiders longest volunteers to help the army in its efforts to quell the raiders. Effrim, Misty, and Duronda continue not to talk, and one day, they are picked up by an officer from District Eight who says that there is a warrant out for them from Twelve, and they are required to go with him.
Effrim: a thirteen-year-old boy who is a good shot and has a wonderful singing voice. He's devoted to his father, and to his barely-remembered mother. He hates how the merchants and miners are at each others' throats, but doesn't feel like he can do much about it. He constantly feels like the girls keep taking control of his quest, but he's a practical boy, and realizes that three heads are better than one.
Misty: His sort-of girlfriend, though neither of them precisely acknowledges this. She's a budding engineer, and always wants to know about machinery. She's also the go-to girl for plans. During their original wandering, she takes Effrim's offhanded suggestion that he'd do better with a bow to heart, and builds him a fairly decent one, given their lack of materials. Everyone agrees he should be the one to carry it, though.
Duronda: At fifteen, Duronda is angry and sarcastic about most of what she encounters. She has the most trouble with the raiders, and by the time they escape, she's about ready to do murder. She will later become Twelve's first victor.
Pappy Angus Abernathy: A very old man who is a sort of honorary grandfather to everyone in the district. When he was a child, his father gave him an old dictionary, which is the one Haymitch (the grandson of Angus's great-grandson) has later on. He resists Thirteen's arbitrary rules until they start whipping his grandchildren for coming to his defense, and he never stops grumbling. His land is used for community farming.
Peet Mellark: The former apothecary, before Thirteen declared herbalism to be superstitious nonsense and forbade him to practice (not that this stops him). His son, Carrig, has married the bakers' daughter, and gone into that business. Peet is Danny's great-grandfather. He and Angus friends.
Spicer James: The oldest of the children in the raider camp. He has developed some protective coloration to stay safe, and Duronda doesn't trust him at first, but Effrim does, and it's his instinct that's right. During the escape, Spicer is instrumental in getting them out, and offers his services to the army to get them free.
Juliana: A Capitol girl whose parents were the liaisons to District Two when that district joined the rebellion. The rebels threw her parents into a pit and stoned them, so her attitude toward the districts is very sour, at least until she's rescued and her return to the Capitol is arranged by the rebel soldiers. She finally befriends Duronda, and tells the Capitol soldiers that the rebels treated her decently.