“Now, Watson,” said he, “we have picked up two clues this morning. One is the bicycle with the Palmer tire, and we see what that has led to. The other is the bicycle with the patched Dunlop. Before we start to investigate that, let us try to realize what we do know, so as to make the most of it, and to separate the essential from the accidental.”

“First of all, I wish to impress upon you that the boy certainly left of his own free-will. He got down from his window and he went off, either alone or with someone. That is sure.”

I assented.

“Well, now, let us turn to this unfortunate German master. The boy was fully dressed when he fled. Therefore, he foresaw what he would do. But the German went without his socks. He certainly acted on very short notice.”

“Undoubtedly.”