On a trip to Prague to visit an exhibition of precious objects of alchemy, Lorenzo Aragona finds himself caught in the dark murder of an old antiquarian, also fond of mysteries. He is suddenly catapulted into a hidden and disturbing world, run by a mysterious brotherhood that will force him to return to Naples.
Helped by the Masons in the deciphering of a series of puzzles, but under the blackmail of shady figures who are threatening to kill him and those he holds dearest, Lorenzo finds himself in front of a real alchemic puzzle, which brings him back to studying the experiments of the famous Prince of Sansevero, who lived in Naples in 1700.
The recovered traces, however, lead him away from his city, to France, looking for a stunning cathedral, containing nine mysterious mirrors. But what is this cathedral and what powerful secret is it hiding?