"But why?" he asked. "Who is he--what do you want with him? What's it all about?" "Oh, find him!" she exclaimed. "You don't know how important it is! If I lose sight of him now, I'll very likely never see him again. And he must be found--and stopped--for your sake!" They had come to the end of the platform, by that time, and Lauriston looked left and right in search of the man described. Suddenly he twisted Zillah round. "Is that he--that fellow talking to another man?" he asked. "See him--there?" "Yes!" said Zillah. She saw the man of the platinum stud again, and on seeing him, stopped dead where she was, holding Lauriston back. The man, leisurely smoking his cigar, was chatting to another man, who, from the fact that he was carrying a small suit-case in one hand and a rug over the other arm, had evidently come in by the just-arrived express. "Yes!" she continued. "That's the man! And--we've just got to follow him wherever he goes!" "What on earth for?" asked Lauriston. "What mystery's this? Who is he?" At that moment the two men parted, with a cordial handshake; the man of the suit-case and the rug turned towards the stairs which led to the underground railway; the other man walked slowly away through the front of the station in the direction of the Great Northern Hotel. And Zillah immediately dragged Lauriston after him, keeping a few yards' distance, but going persistently forward. The man in front crossed the road, and strode towards the portico of the hotel--and Zillah suddenly made up her mind. "We've got to speak to that man!" she said. "Don't ask why, now--you'll know in a few minutes. Ask him if he'll speak to me?" Lauriston caught up the stranger as he set foot on the steps leading to the hotel door. He felt uncomfortable and foolish--but Zillah's tone left him no option but to obey. "I beg your pardon," said Lauriston, as politely as possible, "but--this lady is very anxious to speak to you." The man turned, glanced at Zillah, who had hurried up, and lifted his slouched hat with a touch of old-fashioned courtesy. There was a strong light burning just above them: in its glare all three looked at each other. The stranger smiled--a little wonderingly. "Why, sure!" he said in accents that left no doubt of his American origin. "I'd be most happy. You're not mistaking me for somebody else?" Zillah was already flushed with embarrassment. Now that she had run her quarry to earth, and so easily, she scarcely knew what to do with it. "You'll think this very strange," she said, stammeringly, "but if you don't mind telling me something?--you see, I saw you just now in the station, when you were feeling for your match-box, and I noticed that you wore a platinum stud--with an unusual device on it." The American laughed--a good-natured, genial laugh--and threw open his coat. At the same moment he thrust his wrists forward.