Ruthie is a strong, confident, kind, and happy 10-year-old girl at the beginning of the novel. She lives in a one-bedroom apartment in Queens, a borough of New York City, having recently emigrated to America from Cuba with her parents and brother Isaac. At P.S. (Public School) 117, Ruthie is in a remedial class until she convinces the teacher of her aptitude in English by spelling the word “commiserate”; she then joins the regular class. Her friends include Ramu from India, Danielle from Belgium, and US-born Ava and June. Ruthie wants her family to find happiness and contentment in America, as her mother frequently becomes sad and homesick for Cuba.

Everything in Ruthie’s world changes when a car accident immobilizes her in a body cast for months. The resulting changes to her lifestyle threaten not only her independence, but also her modesty and privacy; she also fights boredom and struggles against the hateful feelings she has for the boy who caused the accident. Her relationship with her mother grows strained, since Mami initially resents the role she must play in tending to Ruthie.

Despite these conflicts, Ruthie remains eager to work hard at her studies and also learns to paint—a new hobby inspired by neighbor Chicho.