Though most of the novel takes place in the late '80s, when Codi and Hallie are adults, it opens in flashback. Doc Homer, daddy of the Noline girls, remembers his daughters Hallie and Codi when they were kids. They slept so close that "no light could show where one body ends and the other begins" (1.2). These two have been besties since childhood, so when we learn in Chapter Two that the grown up Hallie Noline has just left her sister to go farm with the revolutionaries in Nicaragua, we know how devastated Codi must be.
Codi moves back to Grace, Arizona, from big-city Tucson, leaving her now ex-boyfriend Carlo behind. In Grace, she'll teach high school and take care of her father Homer. He used to be the town doctor, but these days, Alzheimer's is causing him to forget who's dead, who's pregnant, and where he put his lunch.
Even though it's where she grew up, returning to Grace isn't exactly a happy homecoming for Codi.
In fact, Codi hated her childhood in Grace.
The town's Spanish-speaking, mother-having kids always made her feel like an outsider. In part, she is one: everyone in the town of Grace is related to the nine Gracela sisters—everyone except for Codi's family, the members of which Doc always said moved there just a generation ago from Illinois.
Unwilling to live with her dad, Codi moves in with her one and only friend from childhood, Emelina Domingos, and gets a job teaching biology at the local high school. She's addicted to travel and plans to stay in Grace for no more than a year.
Over the course of that year, though, Codi starts to build relationships, first with Emelina, then with Loyd, her high school ex-boyfriend. Loyd is smart, patient, and handsome, an Apache with the best dog in the world. Even so, things are complicated between them. (Major spoilers here.) Codi has never told Loyd (or actually anyone—not even Hallie), that when they were fifteen, Loyd got Codi pregnant, and then she miscarried the child. She's been living with the loss of that baby all her life, and it's part of what keeps her from fully investing in her relationship with Loyd.
Talk about drama.
In the meantime, while taking her students on a field trip to the town's river, Codi discovers that the river is dying because of acids dumped into it by the Black Mountain mining company. The bad water is killing the town's fruit orchards, without which the town as a whole will wither up and disappear. Codi accepts this nasty fate as sad but inevitable. After all, Hallie is the activist, while Codi sees herself as more of a lame, boring person who doesn't care about anything.
But then Codi meets the Stitch and B**** club—a bunch of older ladies who knit doilies and make trouble like some kind of older-adult motorcycle gang. Instead of blowing stuff up, they enlist Codi to help save Grace from the mining company by selling hundreds of peacock piñatas designed to spread the story of their town. Codi helps out, and in the process, she learns that she and her family aren't outsiders, after all.
It turns out that Codi has every right to think of herself as a part of Grace. In fact, her father's family is related to one of the original Gracela sisters. The Nolines are the black sheep of the family, though, and so Homer moved to Illinois, changed his name, and tried to erase his family's connection to the town. He kind of confused things, however, by then moving his entire family back to Grace and raising his kids there. Way to send those mixed signals, Homer.
Just as things are going really well for Codi—she's got a loving boyfriend, great friendships, and a job she's awesome at—disaster strikes. Hallie is kidnapped in Nicaragua, and despite everything that Codi tries to do to free her, Hallie is killed.
Codi tries to run away from Grace—and from her grief. She plans to move to Colorado with Carlo, even though his only redeeming feature is his awesome eyebrows. But fate intervenes: Codi's plane won't fly. She ends up in the arms of Loyd, and she does her grieving in the company of the entire town. The book ends with a look into the future, where Codi and Loyd are once again pregnant—and this time they both know it.