He smiled as he thought how easily Giovanni would find the place, and how grievously disappointed he would be when he realised that it was empty.
It occurred at once to Zorzi that Giovanni's first impression would naturally be that Zorzi had taken the book himself in order to use it during the master's absence; and this thought perplexed him for a time, until he reflected that Giovanni could not accuse him of the deed without accusing himself of having searched for the box, a proceeding which his father would never forgive.

Zorzi did not intend to tell the master of his conversation with Giovanni, nor of his suspicions.

He would only say that the hiding-place had not seemed safe enough, because the stone gave a hollow sound which even the boys would notice if anything fell upon it.
But for Nella, it would be safest to give the box into Marietta's keeping, since no one could possibly suspect that it could have found its way to her room.

At the mere thought, his heart beat fast.

It would be a reason for seeing her alone, if he could, and for talking with her.
He planned how he would send her a message by Nella, begging that he might speak to her on some urgent business of her father's, and she would come as she had come before; they would talk in the garden, under the plane-tree, where Pasquale and Nella could see them, and he would explain what he wanted.