“Thank you, monsieur. But, for the moment, I do not propose to leave Boulogne.”

“What?”

“No, we will enter this hotel here, by the quay.”

He suited the action to the word, demanded and was accorded a private room. We three followed him, puzzled and uncomprehending.

He shot a quick glance at us. “It is not so that the good detective should act, eh? I perceive your thought. He must be full of energy. He must rush to and fro. He should prostrate himself on the dusty road and seek the marks of tyres through a little glass. He must gather up the cigarette-end, the fallen match? That is your idea, is it not?”