Sergio Marquina, or better known as "the Professor", the leader of Spain's biggest robbery, spent most of his childhood and adolescence in the San Juan de Dios hospital in San Sebastián. There he made friends with Jero Lamarca.

During Jero's most difficult days, Sergio, who was already exceptionally intelligent, invented puzzles for him to distract him from his illness. When Sergio's vision became dim, Jero steered him back: he taught him to fold paper birds.

A little time has passed since the robbery of the State Treasury. Jero is gathering his few belongings in his motorcycle repair shop, which he is forced to close when he receives a package. It contains an unsigned letter, a notebook, a small box with a padlock, a photograph, a Dali mask and a red paper bird.

Jero can have no doubt. Somewhere out there, Sergio has hidden some of the loot for him so he can start a new life. You just have to follow clues to find it.

And you?

Can you play it all the way through?

The professor's diary also provides exciting new details, while presenting its readers with fun puzzles, all of which are colored by photos of the series' favorite characters.

A must read for all fans.