San Juan de Puerto Rico, fall of 1520. Juan Ponce de Leon, conquistador and first governor of the island, plans his second voyage to Florida, discovered and named by him seven years previously. Officially, his aim is to found the first city in this territory, of which the Spanish Crown has appointed him as its Adelantado, with powers that would make him in the first European to politically govern at his destination. But, secretly, at the same time, he is also planning to reach the Fountain of Eternal Youth, taking advantage of the information that he has accumulated after his conversations with several native caciques on his travels through the Caribbean archipelago. However, the objective that he decides upon when reaching it, and the motives that drive him, would surprise anyone. Ponce intuitively knows that this could be his last voyage. And among the other consequential decisions, he puts his personal papers in order, with which he would be able to rebuild the altarpiece of his life, the last panel of which would be precisely that voyage he is about to undertake. As he does so, his life appears before him, at its most significant moments, but also interwoven with the history of Spain (and that of the Americas), captured during a transcendental period and including some of the most intimate and unknown moments. All of this is a result of having been close to the main characters, starting with the Monarchs, Ferdinand and Isabel, from when he escorted them as a very young pageboy when they exchanged their marriage vows in secret whilst persecuted within Castile, something they never forgot and endeavoured to grant him a very special treatment, particularly during the most difficult personal and political times of his life.