Living in Katwe, a slum in Kampala, Uganda, is a constant struggle for 10-year-old Phiona, her mother Nakku Harriet, and her younger family members. She and her younger brother help their mother sell maize in the market. She also helps care for her baby brother. Her world changes the day she meets Robert Katende at a missionary program. Katende coaches soccer and teaches children to play chess at a local center. Curious, Phiona visits the center, learns the game, and becomes fascinated with it. She becomes a top player in the group under Katende's guidance.