I jumped out and looked around. No cab in sight. “Well,” I said to Dorothy, “here’s a pretty go. Nobody in sight, and I don’t know which is the house.” Without a word, Dorothy leaned forward and whistled a single bar. Out of the fog came the notes repeated, and a moment later across the street came Tom. “Oh, you’ve reached here finally, have you?” said he, a trace sarcastically. “I thought you’d never arrive; I couldn’t imagine what kept you.” As he spoke, I heard a sort of choked gasp from the top of the hansom, but fortunately Dorothy’s suspicions were not aroused. “It hasn’t seemed so very long,” she answered simply, to which Tom responded, “Oh, really, hasn’t it?” as he took her arm to lead her across the street. He called back to our cabby as we left, “Drive forward a little, and you’ll find a sort of shelter where you can wait. The other cab’s there.” “Right, sir,” came the reply, and we heard the slow movement of his disappearing wheels, as we three were left in the ocean of fog. “Swenton’s hunting up the caretaker,” said Tom. “Hamerly and I have been waiting for him to come back. The old rooms are locked up tight.” We found Hamerly in a vestibule where a single gas lamp flickered, and, as we waited, we fell to talking in low tones. The mist seemed to bring our voices to a minor key. Perhaps ten minutes had passed, when the door opened, and Swenton entered, accompanied by a man in a coarse ticking apron. “This is the caretaker, sir,” he began, bowing to Dorothy and me. “He refused to let me in to get my things. Says the laboratory was left after Dr. Heidenmuller’s death to another chemist, a gentlemen who bought all the doctor’s stuff from the heirs. He was there, off and on, for a little while, but he went away quite a long time ago,--went one night suddenly and never came back. This man says the agents won’t allow anybody in. I brought him here, so you could talk to him if you wished.” The caretaker stood silent and sullen as Swenton spoke, his hands deep in the front pockets of his apron. “I do want to speak with him,” said Tom briefly. “Come here,” and he led the way apart, the caretaker following. A moment’s conversation was broken only by a golden clink, accompanied by the jingle of keys, after which the caretaker disappeared, and Tom turned back to us. “I have here,” he said mysteriously, “a bunch of keys which I strangely found on the floor in the rear of this hall. Suppose we ascend to the top floor and see if they will work there.” Dorothy’s face was clouded as Tom came up to the spot where we were standing a little apart, Hamerly and Swenton had already started up the stairs. “I’m not sure that you are doing right in this, Tom,” said Dorothy swiftly, in a low voice. “I don’t like to bribe a servant to let us into a place where we don’t belong.”