A long time after the heist of millions at the National Mint of Spain, and while the noise of the sensational case has begun to fade, a strange package is delivered to Hero Lamarca on the day he is gathering his last belongings from the neighborhood workshop he had been running until then.

Inside, he will find an unsigned letter, a notebook, a locked box, a photograph of a mask with the face of Dalí, and a bright red origami. Hero has no doubt about the sender. Sergio Marquina, widely known as "The Professor" and mastermind of the biggest heist in Spanish history, is none other than his childhood friend, the one who came up with puzzles during the dark days they spent together in the San Juan de Dios care facility in San Sebastián.

He is the clever boy whom Hero taught the art of origami to make him smile every time he saw his eyes welling up. It is clear that Sergio, missing and wanted by the authorities since the day of the heist, has planned a well-hidden place for his childhood friend to find the loot. All Hero has to do to get there is solve the puzzles. And you? Will you manage to reach the end with him?