"You see," said Bob earnestly, "I happen to be more closely connected with it than you are. You have no human relation with the parties in the affair, who, until quite lately, were complete strangers to you. I have some sort of connection with them through my nephew Ronald, whom I have seen to-day, and who, I may tell you, is troubled by the inquiries you have made of him. He has no notion of their tendency, but he felt that something is being concealed from him which he has a right to know. It is in his interests, and for his satisfaction, that I enter into a direct partnership with you. Have you succeeded in persuading your good wife to go to the seaside?" "I have, and she will be away for at least for a fortnight; if necessary I shall insist upon her remaining at Brighton for a longer time." "So that we are free to set actively to work without interruption." "Yes, Bob. How about Barbara?" "My landlady takes her upon trial. There will be no charge for board and lodging, and if she gives satisfaction she will get a shilling a week to commence with." "I am glad to hear it. And now to get back to your suspicions that Mr. Nisbet may be concealed in the house even while we are talking. He might endeavor to get rid of us, you said. When, and how?" "When? In the dead of night, when we are sound asleep. How? Well, I put together these facts: Mr. Nisbet's knowledge of dangerous chemicals, the narcotic which Ronald informed you he gave to his stepdaughter, and the significant conclusions which can be drawn from your conversation with Dr. Cooper. I propose, not this evening, to-morrow morning, that you, or we together, pay a visit to Dr. Cooper, and have an interview with him. He has a grievance against Mr. Nisbet; it might be turned to effect." "You suspect him of being an accomplice?" "In a certain sense. What do they call it in law? Accessory after the fact. He might have known nothing at the time; the belief that his knowledge of poisonous narcotics--bear in mind his boast--had been used to a bad end may have come afterward." "But if he makes any admission it could be used against himself." "It could, but he may be able to prove his innocence of a guilty intention. However, that is a point for future consideration. A visit can do no harm. He is desperately poor, and a little bribe may tempt him; if we cannot worm anything out of him, we may out of his wife. Now, Ned, before I consent to sleep in this house I intend to search it thoroughly from roof to cellar." We carried out this proposal; we thoroughly examined every room, we made fast every door when we closed it behind us; and we discovered nothing. Our search over, we were quite convinced that we were the only persons in the house.