A Long Walk to Water begins as two stories, told in alternating sections, about two eleven-year-olds in Sudan, a girl in 2008 and a boy in 1985. The girl, Nya, is fetching water from a pond that is two hours' walk from her home: she makes two trips to the pond every day. The boy, Salva, becomes one of the "lost boys" of Sudan, refugees who cover the African continent on foot as they search for their families and for a safe place to stay.

Enduring every hardship from loneliness to attack by armed rebels to contact with killer lions and crocodiles, Salva is a survivor, and his story goes on to intersect with Nya's in an astonishing and moving way. Includes an afterword by author Linda Sue Park and the real-life Salva Dut, on whom the novel is based, and who went on to found Water for South Sudan.