Set entirely on Earth, the Leftover Girl tells the story of the Alpha Mission and the century that produced it from the point of the view of two characters, Helen, a scientist working for the organisation who goes on to play a leading role, and Marta Camacho, one of the Mission Children. Known as Tata, Miss Camacho is one of the ‘spares’, created as a back-up should anything unfortunate happen to her model, the world-famous Marta da Guia. But Tata is not content to wait around for that eventuality and takes her life into her own hands.