Esperanza Ortega, the daughter of wealthy landowners, lives in Aguascalientes, Mexico, in 1930 on her family's ranch with her mother, father, and grandmother.
The day before Esperanza's 13th birthday, her father is murdered while working on the ranch. At her birthday party, she receives a doll from him. It was her last gift from him. Her uncle Luis reveals that he now owns their land. He offers to continue to care for them and their ranch if Esperanza's mother, Ramona, will marry him. When she refuses, he burns down the ranch. Esperanza's grandmother, Abuelita, is injured during the fire and is sent to a convent where she can recover. Esperanza and the rest of her family decide to travel to the United States.
When Esperanza's family arrives in the United States, which is currently in the grip of the Great Depression, they settle in a farm camp in Arvin, California. Esperanza begins to adjust to her new life, but still fantasizes about Abuelita rescuing her from poverty.
Ramona contracts Valley fever, and the doctors are unsure if she will survive. Esperanza, desperate for money to support herself and pay her mother's medical bills, takes work on the farm camp despite being underage. She stockpiles money orders in the hopes of one day sending them to Abuelita and allowing her to travel to the United States.
Tensions rise in the camp as migrants from Oklahoma flee the Dust Bowl and look for work in California. Some workers go on strike to try to improve working conditions. Following a massive demonstration by the strikers, the farm owners call immigration officials to round up and deport the demonstrators. However, many of the people deported were natural-born American citizens who had never been to Mexico. Esperanza has a breakdown and then an argument with her friend, Miguel, because of this event. The next day, they find that Miguel has left to seek work in Northern California.
When Ramona recovers from her illness, Esperanza proudly goes to show her mother the money orders she saved, only to discover that they are missing; Miguel took them when he left. However, Miguel used them to secretly travel to Mexico and retrieve Abuelita.
The book ends on the day of Esperanza's 14th birthday, and Esperanza has finally learned to be grateful for what she has: her family reunited, friends who love her, and most of all: hope. (Esperanza means "hope" in Spanish.)
