Dan went to bed with an aching head, doubtless induced by the power of the drug which had been used to stupefy him. The Sumatra perfume was evidently both powerful and useful, as it was used by the Society of Flies not only as a means of recognition in the form of a harmless scent, but as a soporific to bring about insensibility. Probably many a person had been rendered unconscious by the drowsy smoke, and taken to the headquarters of the infernal association, there to become members. But where the headquarters were to be found, Dan had not the slightest notion. And, as his head pained him greatly, he decided to wait until the next morning before thinking out the matter. Off and on he managed to sleep a trifle, but it was not until the small hours that true slumber came to him. It was nine o'clock when he woke, and then he found his head clear, and the pain absent. Only an evil taste remained in his mouth, and after a cold bath he felt more himself, although a touch of languor remained to recall to his recollection what he had been through. After breakfast he lighted a pipe, and began to think over late events as carefully as was necessary. On alighting at his own door he had paid the driver of the four-wheeled cab, and had asked questions, which the man was willing enough to answer. Halliday hoped by learning where the cabman had picked him up, to discover at least the neighborhood wherein the headquarters were situated. It was difficult to think that an unconscious person, as he had been, could have been taken any great distance along streets, or roads, or lanes, without attention being attracted. But the cabman explained that the friend who had placed his fare in the four-wheeler, had removed him from a taxi, which the friend declared had broken down. "And he wanted to get you home, you being drunk," explained the driver, "so he shoved you into my trap, and I drove off, having the address I was to take you to, leaving your friend to look after the broken-down taxi, along with the chauffer." From this explanation it was apparent that on being removed from the dark room Dan had been transported for some distance, long or short, in the taxi. He did not believe that the same had broken down, but that his friend--probably Marcus Penn--had hailed the first cab he saw, and on pretence of an accident had got rid of him in this clever way. It was West Kensington where this exchange had taken place, according to the cabman's story, but since he had been driven an indefinite distance by Penn in the taxi, the headquarters might be in Hampstead, or Blackheath, or Ilford, or, indeed, anywhere round about London, if not in the heart of the metropolis itself. All bearings were lost by the clever way in which the return had been carried out.