"The year 1532, Barcelona, Spain, in the rain..."
So begins the story of Esteban, a young orphan of 12 years. Raised by Father Rodriguez, his main hobby is to listen to the stories of sailors in the taverns of the port, returning from distant and mysterious countries. And that day, two sailors, Sancho and Pedro, explain that they must leave the next day aboard the Esperanza to the New World in search of towns entirely built out of gold. They want to persuade the other to sail to the Eldorado, but they are skeptical!
On these facts, a messenger from the Queen enters the tavern in search of Esteban. As it should be noted Esteban is not a child like any other: he is famous in Barcelona for the gift of calling out the sun: he is the "son of the sun".
All the sailors go looking for him. All but Mendoza, a navigator who must also go to the New World in search of its treasures. Mendoza seems interested in Esteban who runs away, pursued by sailors, but he is finally caught and perched on top of a mast in the port to call the sun. He does not believe in its alleged gift but the sun finally come back to the general satisfaction and for his greatest surprise.
He is then summoned to see Father Rodriguez, his adoptive father, who is very ill and wishes to see him on his deathbed ... Father Rodriguez then tells the story of his origins. Esteban was found 12 years ago when his boat sank because of a storm. In the sinking, his real father disappeared but Mendoza, a sailor, saved him. He wore already a mysterious gold medallion around his neck, representing the sun. Mendoza, who hears the story of Father Rodriguez understands that he has finally found the child he saved years ago. Father Rodriguez finally dies; Esteban is mad with grief, having lost the person he loved most in the world ...
Mendoza told him who he is and he proposes to sail with him for the New World in search of his origins and Cities of Gold. He has also half of the medallion of Esteban, substituted during the sinking, and which has a mysterious connection with these cities and with his father. Esteban hesitates but finally decides to go on an adventure, hoping to find his father.
The next deay is the big day, while the port is in jubilation. Esteban is hidden in the hold of the Esperanza. He then discovers, gagged in a crate, a young Inca girl, named Zia. She was abducted from his village by the Spanish to lead them to the secret Cities of Gold. Both are about to experience the greatest adventure of their lives ...