"You will remain here," I said to him, "and keep Dr. Pye's house under observation, without drawing attention upon yourself, till I return. I shall be back in less than half an hour. Report to me if any person enters or leaves the house during my absence." When I returned it was in the company of an officer in plain clothes, whom I had instructed to keep watch on the house until I sent another man to relieve him. Applebee reported that Dr. Pye's street door had not been opened. Well, the train is laid. When it is fired, if friend Joseph Pitou is not following a will-o'-the-wisp, there will be a rare explosion. Even if he is, I think I can promise one. What annoys me is, that I have been unable to get the particulars of the case of Louis Lorenz. A postman's knock at the door! The telegram! Yes, here it is: "Letter, in French, to-morrow. Pitou." CHAPTER LVII. DETECTIVE LAMBERT CONTINUES HIS DIARY. On Monday morning Detective Lambert, as recorded in his diary, received Joseph Pitou's letter from Milan--this time written in French, which, being duly translated by Mrs. Lambert, caused the English detective profound astonishment and delight. It was in keeping with the literary methods he pursued that he did not insert the letter in his diary, and gave no intelligible account of its contents. Neither would it have been in accordance with his methods to have omitted mysterious reference to it: "Letter from Joseph Pitou, commencing, 'My Very Dear and Very Illustrious Compatriot and Brother-in-arms,' which I look upon as foreign bunkum. I don't object to the 'illustrious,' but we English would have put it differently. "If I were not so closely mixed up with the Catchpole Square Mystery I should regard friend Joseph's letter as being copied out of a romance. It reads like romance. But it isn't; it is a chapter, or several chapters, out of real life. It is a feather in one's cap to be connected with such a character--not friend Joseph, but the game we are hunting. Big game. The idea of coming face to face with it is enough to scare a timid man, but that kind of risk doesn't scare an Englishman. I won't do friend Joseph the injustice to say it might scare him. "He sends me the portrait of Louis Lorenz. The mischief of it is that Lorenz's face is covered with hair--a fine crop which in the present instance, I do not admire. When a criminal is condemned to death in Gallicia don't they shave him? A felon loses his rights as a citizen, and his moustachios and whiskers are the property of the State. "My man is clean shaven, but the blue shade on his chin and cheeks show that he has a fine stiff crop of his own. So have hundreds of thousands of other men. Still it is a link, though not a strong one.