Sergio and his little brother Divino are poor children who live in a favela in the populous city of Sao Paulo, Brazil. When they lost their mother, Dona Ute - a teacher who has a little school in that place - took them to live with him.

They are now on vacation in a wilderness area not far from the city. Looking for firewood to light the kitchen stove, the little brothers go into the mountain where they unknowingly go through a dimensional door, The Magic Mound, and appear in the kingdom of Maxa. There they are greeted by Mara and Mamara, princess and queen, who tell them the wonderful story of vitaluz, the elixir of immortality that, however, implies that those who take the elixir can no longer have children.

They ask the brothers to rescue Mireya, a girl also from Brazil, from the power of King Alaram; For this they have the collaboration of Platero, a donkey as nice as he is stubborn, and a mysterious little man called Tamoshot. The search for Mireya is a dangerous adventure, but it gives them the opportunity to learn many important things about life.