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