Taylor is born in Kentucky with the name Marietta Greer. In her hometown, she went by Missy, which grew out of her childhood insistence that her name was Miss Marietta. She assumes the name Taylor when she leaves her hometown, adopting the name of the town where her car runs out of gas. Taylor is a smart, determined young woman who is dissatisfied with the kind of life available to her in her hometown, where young women tend to fall pregnant, drop out of school or work, and be forced into unhappy marriages. Inspired by a lifetime of her mother telling her how smart and special she is, Taylor sets off cross-country to search for something more. She is prepared for setbacks, but not for the responsibility of having a young child thrust into her care. Taylor's conscience, however, won't let her do anything but her best for the child, whom she names Turtle. Taylor's resilience is tested as she continues westward and settles in Tucson when her tires wear out. She builds a life there with fellow Kentucky transplant Lou Ann, as well as a cast of largely female friends and supporters. When Turtle is threatened, Taylor's confidence falters, but she eventually rallies and makes a conscious decision to take on the responsibilities of being her mother, with a network of women to help her.
Turtle is a three-year-old Cherokee girl whose aunt gives her into Taylor's care. Her aunt fears for the girl's safety and takes a chance that the child will have a better life with Taylor, even though the two women have never met before. Turtle is the name that Taylor gives her because the child doesn't speak, and they do not learn her real name until months later. Lou Ann discovers that the girl's real name is April when she says the name of the month and Turtle responds. Turtle suffered severe physical abuse at the hands of someone in the years before Taylor knew her. Dr. Pelinowsky's examination of her x-rays show healed bone fractures and a period of stunted growth that makes the child appear a full year younger than her true age. With Taylor, Turtle blossoms, gaining weight and eventually beginning to laugh and speak. Turtle adores planting in the garden with Mattie and mostly speaks about vegetables. Later, when Taylor is away and Turtle is in the park with Edna, a stranger tries to abduct the child, and Edna fights him off. Turtle recovers, but a social worker gets involved and notices that Taylor has no claim to the child. When Taylor takes Turtle back to Oklahoma to try to secure legal custody, the child reveals that she saw her mother buried, explaining a further trauma in the toddler girl's life. Taylor is eventually able to gain custody of Turtle, and they return to Arizona together.
Lou Ann Ruiz moved to Tucson from Kentucky after she married Angel Ruiz. She fell in love with him when he was a young rodeo cowboy, but their relationship changed after he was in a car accident that resulted in the loss of one of his lower legs. When Lou Ann became pregnant with their son, Dwayne Rae, their relationship was already quite difficult. She was a little bit lost when Angel left her with no warning, while she was seven months pregnant. Lou Ann has little confidence in herself and does not view herself as an especially capable woman. She prefers to let things play out and has a hard time standing up for herself. Lou Ann even asked Angel to move back in when her mother and grandmother visit after Dwayne Rae's birth, so that she won't be forced to move back to Kentucky with them. In this case, Lou Ann makes the decision to live on her own, but presents it as an inability to endure conflict and stand up for her decisions. Living on her own and then with Taylor forces Lou Ann to take on an independence she has not previously had. She takes a job, which she is good at, and gains some confidence there. She is happy enough in her life to resist the temptation of moving to Montana to rekindle her relationship with Angel. She is even daring enough to begin a new relationship with a new man while Taylor is away. Lou Ann grows into herself throughout the book, casting off the lack of confidence and dissatisfaction caused both by her lifelong relationship with her highly critical female family members and by her failing relationship with Angel.
Mattie is a complex, principled woman who acts as a kind of surrogate mother to Taylor. She is kind and generous when Taylor arrives at the garage in need of help with her tires and, Mattie can tell, with her parenting. Mattie gives Taylor advice and assistance freely and, later, offers her a job at Jesus Is Lord Used Tires when she needs it. She even helps Taylor to overcome her fear of exploding tires. Mattie is simultaneously leading a double life that is, at first, only hinted at. In the upstairs rooms of her home, attached to the shop, Mattie runs a sanctuary for illegal immigrants who are moving along an underground railroad further into the United States, trying to find safety from immigration officers. Mattie speaks out on television on behalf of immigrants while running a shadow network of drivers and sourcing health care for those who need it. Mattie comes to care deeply for both Taylor and Turtle and introduces them to Estevan and Esperanza, two of the immigrants that she helps. Mattie treats Taylor and Turtle just the same as Estevan and Esperanza, considering all of them to be refugees of one sort or another. She is both touched and worried when Taylor decides to take on a portion of her role helping immigrants by volunteering to drive Estevan and Esperanza to a sanctuary in Oklahoma.
Estevan was an English teacher in Guatemala, before he was persecuted for his role in a teacher's union. He speaks Spanish, but he is native Mayan, from a tribe that speaks a different dialect from his wife Esperanza. Estevan and Esperanza were both members of the teacher's union, and their daughter Ismene was taken from them to try to get them to identify other members. In Tucson, Estevan works in a Chinese restaurant, taking his change in circumstances in stride and enjoying the small pleasures of his new life. He loves his wife dearly, but she is not able to move on as easily from the trauma they suffered. Through Mattie, Estevan meets Taylor, Turtle, and Lou Ann. He and Taylor have a connection that deepens when his wife Esperanza tries to commit suicide, and he shares the details of their past with Taylor. Estevan comes to care deeply for Taylor but remains faithful to his wife. He and his wife are both close friends with Taylor and are deeply grateful for her offer to drive them to a sanctuary in Oklahoma to avoid deportation. After several days together in the car and at the Grand Lake o' the Cherokees, Estevan and Esperanza agree to pretend to be Turtle's Cherokee parents in order to legally transfer custody of the girl to Taylor. Upon safely reaching the sanctuary, Estevan says a heartfelt farewell to Taylor, knowing that he will never see her again.
Esperanza is the wife of Estevan and both of them were teachers in Guatemala. Esperanza is Mayan; she learned Spanish as a second language and also understands and speaks English, although rarely. Esperanza and Estevan had a daughter, Ismene, who was taken by the government in an effort to make her parents reveal the other members of their teacher's union. Esperanza is deeply affected by the loss of her daughter, even though they believe Ismene is still alive and has been given to a childless military or governmental couple. Esperanza suffers from depression as a result of her loss, and she tries to commit suicide but is taken to the hospital and saved by Mattie. Esperanza begins to reawaken during the drive from Tucson to Oklahoma as she interacts with Turtle in the backseat of the car. They become close during the ride, and Esperanza is determined to help Taylor gain custody of Turtle by posing as her Cherokee mother, with Estevan as her father, before the notary public. Pretending to be a mother to Turtle and transferring custody of the girl to another mother is a cathartic experience for Esperanza, helping to release her suppressed emotions about the loss of her own daughter.