In the summer of 1643, in the South Seas, a young Piedmontese man, Robert de la Grive, arrives as a castaway on a deserted ship. The ship is full of unknown animals and strange machines and devices, and before it, close and unreachable (not only, we will later discover, in space, but also in time), lies a dream island. Robert writes letters to the "Lady"; through which his past is gradually revealed: duels, sieges, love affairs, convoluted salon disputes. It is, in fact, a slow and traumatic initiation into the world of the new science, the reasons of state, the espionage networks of Mazarin and Richelieu, the Thirty Years' War—in short, into a cosmos in which the Earth has ceased to be, for many, the center of the universe. In this 'Sea of ​​Innocence' nothing is innocent, and Roberto knows it from the beginning, because he has come to these Antipodes to solve - without personally wanting to - the mystery over which the new powers of the time are struggling: the secret of the Fixed Point.