In the City he was constantly expressing his regret at the unfortunate deaths of his partners, Count de Chamartin, of Madrid, and the Baron van Veltrup, of Amsterdam, but he had expressed himself ready to carry the great deal through himself, though it involved the speculation of nearly two millions sterling. I could hardly take up any newspaper--neither could you, my reader, for that matter--unless I saw De Gex referred to, under another name, of course. He went here and there, the guest of a Cabinet Minister, playing golf with a Leader of the House, or spending a week-end with a Duke, until it seemed that the world of Society had at last prevailed upon the mystery-man of millions to emerge from his shell and take up his position in Mayfair. When I saw that he was the guest of certain hard-up members of the aristocracy, or of war profiteers, who, dropping their aitches, had bought ancestral homes, I merely smiled at the ignorance of those who were entertaining one of the greatest criminals in Europe. In the watch I kept each evening upon the house in Stretton Street my friend Harry Hambledon assisted me. As we lurked in doorways in the vicinity, we saw the great ones of London Society, of both sexes, going and coming, for Oswald De Gex had now commenced to entertain upon a lavish scale. He gave smart dinner-parties and musical evenings, which the most exclusive set enjoyed. One night, after it had grown dark, I sauntered along Park Lane, as was my habit, and having turned into Stretton Street noticed a rather shabbily dressed man, evidently a foreigner, descending the steps from De Gex's door. He turned in my direction, and we came face to face. In an instant I recognized him as the Spaniard, Mateo Sanz! He had never seen me before, therefore, when at a respectable distance, I turned and followed him along to a street off the Edgware Road, where he entered a third-class private hotel. What, I wondered, was his object in visiting De Gex unless some other plot was in progress? I, however, did not intend, now that I knew the truth concerning the death of the Baron in Amsterdam, that the assassin should escape. Hence I took a taxi to Scotland Yard where I was interviewed by a detective-inspector to whom I revealed the hiding-place of the much-wanted criminal. He thanked me, and then began to inquire what I knew concerning him. In return, I told him of my friendship with the great Spanish detective Rivero, and how, with the latter, I had seen Sanz at the station at Montauban. Presently he rose, and telling me he would search for any request from the Spanish Government for the man's arrest, he left me. He returned a quarter of an hour later with some papers in his hands, and said: "I find that the Madrid police have applied to us for this individual's arrest, and here is his photograph," and he showed me one similar to that which Rivero had sent me to Amsterdam.