Extract from the Diario de Vitoria: 

All the cards of the game are already dealt, but I don’t know if you will be able to hit enough to lay them all on the table, Thief of the Deck… or should I call you Mr. and Mrs. Bock…?

This note arrived anonymously to the editorial office of Diario de Vitoria and was published yesterday. This morning, a red envelope with the reply from the thief who has the whole of Vitoria in suspense has not been long in coming: If you think that you and your shoddy detectives are going to be able to stop me, I am sorry to tell you that you are wrong, the Ace of Spades, as you know, we keep it especially for you… a violent greeting. signed: Bock and Mrs. Bock.

My letter to the newspaper bore the exact fruit I had hoped for! Irritated Bock had fallen into my trap and had confirmed two important things to me; on the one hand, that the thief was not one but two, and on the other hand that these were confirmed as Bock and Madame.

This assurance carried my investigations much further and led me in a stroke of luck to the doors of one of their houses, rented in H.B.’s name…. It was not difficult to tie up and after picking the lock like the best of thieves (a good detective must always have his methods) I found myself, face to face, behind a large bookcase with its safe….

Was that where they hid the loot? The idea seemed juicy and attractive? Faced with the impossibility of opening it without a combination, a children’s book caught my attention and my surprise was great when inside that volume full of princesses, knights, dragons and carriages, an annotation could be seen on the side:

When you are at a crossroads, it is important to use your head, but don’t forget your feet, since the combination of both is the key to solve any visible problem.

Would that phrase have anything to do with the combination to open the safe?