"That is a question I cannot answer," I said, "though the probability is that Mr. Nisbet believes himself safe, or he would hardly have gone to so central a hotel as the Chatham; but it is certain that they are proceeding with some degree of caution, or the name of Cooper would have been found in the arrival book. Has any idea suggested itself to you that would be likely to explain the reason of Mr. Nisbet choosing Dr. Cooper as a companion?" "Many ideas have suggested themselves," answered Ronald, "of which I have not yet spoken; but we will follow this one out, to see if we agree. You paid a visit to Dr. Cooper on Sunday evening, and, as his wife said to you this morning, he let his tongue run too freely. Her remark proves that some conversation must have passed between them as to your visit, and that Dr. Cooper recalled--not very distinctly perhaps--what it was he said. My belief is that this conversation took place in the presence of a third party, who was chiefly responsible for it." "Of a third party!" I exclaimed. "The third party," continued Ronald, "being Mr. Oliver Nisbet, who visited the Coopers on the following night. He must have had some motive for this visit, for it is not likely--after what you learned from Dr. Cooper's lips of the feeling he entertained toward Mr. Nisbet--that this gentleman would have paid his accomplice a visit in which there was no direct motive. I speak of them as accomplices because there is no doubt in my mind on the point. Dr. Cooper was bribed to give a false death certificate, false for the reason that he was not in a position to give a true one, and for this service Mr. Nisbet paid him, and made promises (according to Dr. Cooper) which he did not fulfill. Whether these promises were or were not as Dr. Cooper hinted is of small moment in what we are discussing, the one thing certain being that Dr. Cooper labored under a sense of injury, and believed himself to have been wronged. It is more than probable that, in some way, Dr. Cooper conveyed this impression to Mr. Nisbet, and that he was aware of it. This must have occurred years ago, and shortly afterward Dr. Cooper loses sight of his employer, and has no means of communicating with him. If he had known where to write to him he would certainly have done so, in his state of poverty, and would most likely have thrown out some kind of threat. During this interval Mr. Nisbet keeps himself hidden from the man who has served him at a critical time; he has no use for him; all evidence of the crime (the nature of which has yet to be discovered) he has committed is destroyed, and there is only one person in the world who can throw the remotest suspicion upon him; that person is Dr. Cooper, and even he, if he dared take open action, would find himself implicated in the consequences. So matters rest for a considerable time, and we come now to the present. It is on Sunday only that you are informed by the private inquiry agent you employed that Mr.