It was a very pleasant morning, and Marco had the window open; so he could see the boys very plainly.

They stopped on the farther side of the fence which they had got over, and though they were partially concealed by the fence, yet Marco could plainly perceive that they were busily employed in doing something there, though he could not imagine what.

He wished very much to go and see; but he knew that it would be in vain to make request for permission, and so he contented himself with watching them.
Just at this moment his uncle opened the door which led into the little study, and asked Forester if he would step into the office.
Forester did so; and then, after a few minutes, he returned, put up his books, and said that he had got to go away, and that perhaps he should not be back till noon.

Marco had often been left alone at his studies for a time, but never for a whole morning before.

He knew that he was to go on with his work just as if Forester had remained.