What is the gathering blue? explain what happens in the book chapter by chapter...
Kira lives in a harsh civilization where people, although fortunately constrained by a system of rules, have little feeling or compassion for others. Physical imperfection is not tolerated, and parents routinely beat their children, an atmosphere chillingly exemplified in Chapter 17 by the woman in the Fen shoving away the hungry hands of her "tykes" as she greedily eats an apple. It is no accident that, in this atmosphere, Annabella can teach Kira to make all colors of thread except blue, the symbol of peace and calm. Little Matt travels "yonder" and brings Kira a small amount of blue thread, which she will "gather". Kira's "gathering blue" is a sign of hope, that she and those close to her will one day bring to her civilation the ability to become "healing people liv(ing) in harmony" (Chapter 22).
Although it is not broken into chapters, the link below provides an excellent account of what happens in the book.
You can find a free summary for Gathering Blue on Wikipedia