Katniss watches her children, a boy and a girl, play in the field back in 12. They don't know that beneath them are the bodies of all the people who died in the war.
Peeta had to work on Katniss to have kids for a long time before she agreed. Katniss nearly couldn't do it.
Her children are starting to realize about the Games, which are now part of the history they learn about. Katniss isn't sure what she'll tell them about how it all went down. They think their world is totally safe.
Peeta helps her by saying it will teach their kids about courage and about all the people they knew and loved.
Katniss gets through it by thinking about all the good things she's witnessed. But she still can't forget the Games.