I, of course, made no mention of Oswald De Gex, but it suddenly occurred to me that if Sanz were arrested De Gex might take fright, so I suggested that the Spaniard be kept under surveillance until the Spanish police were communicated with. "I believe Señor Rivero suspects that Sanz is one of a very dangerous gang," I said. "If so, it would be well to arrest them all." "Are the others in London, do you think?" asked the tall, dark-haired official of the Criminal Investigation Department. "Ah! That I do not know," was my reply. "I only know that Mateo Sanz is a very dangerous person, who has been wanted for several years." "Well, we thank you very much for your information, sir, and we shall act upon it at once," he replied. And then I went along the stone corridor and out again into Parliament Street, well satisfied that I had, at last, placed one of the criminals in the hands of the police, who would, in due course, learn the true facts concerning Baron van Veltrup's mysterious end. CHAPTER THE TWENTY-SEVENTH A CURIOUS STORY At Scotland Yard they acted upon my suggestion, and at once sent a wireless message to Señor Rivero in Madrid, telling him of the discovery of the notorious Mateo Sanz. In the meantime my curiosity was further aroused by a note sent to me by Mrs. Tennison's servant, Mrs. Alford, next day, saying that Doctor Moroni had called at Longridge Road and that, finding Miss Gabrielle absent, he had put to her a number of questions concerning myself. "As I promised you, sir," the woman wrote, "I pleaded ignorance of everything. He was apparently astonished to find my mistress and Miss Gabrielle away. He asked me for their address, but I replied that they were moving from place to place on the Continent. He seemed most annoyed, and went away." I wondered what was his object in going to Longridge Road, if not for the purpose of some further evil work. Though he pretended friendliness towards Gabrielle, yet I knew that he was her enemy, just as he was mine. Moroni was in London, hence he would no doubt visit De Gex. Hambledon was unknown to Moroni, therefore he watched in Stretton Street on the following night, and in his work of observation he was assisted by Norah, who had been told something of the strange circumstances, though of course not the whole amazing story. Just before eleven o'clock Harry and his fiancée arrived at Rivermead Mansions in a taxi and told me that they had seen Moroni arrive at Stretton Street about half-past nine. He was admitted by a new and rather supercilious man-servant--for Horton did not now seem to be in the great man's employ. "Ten minutes afterwards Suzor arrived," Harry said. "Then about half an hour later Moroni came out."