I knew what was passing through his mind. Quite recently he had become interested in a case which was in my hands. He had opposed my solution of the difficulty with another which contradicted me at every point, and we had almost quarreled about it, when a new fact came to light, proving that he was altogether wrong. Even Christopher Quarles was not infallible. Evidently he had noticed the sarcasm in my voice, and would have me remember how often he had been right. In the Riversmouth case, I argued, the professor was hampered by circumstances. He had got it into his brain that he was called upon to deal with a difficult problem, and very naturally he saw difficulties where there were none. I knew from my own experience that for a detective a preconceived idea is deadly. He can only see things from one point of view. I was convinced this was Quarles's position, and the straightforward evidence given at the inquest next day only confirmed this conviction. If doubt remained in anyone's mind as to the identity of the body, it was settled beyond all question. A large sum of money being involved, the insurance company sent down an official who had seen Dr. Smith when he called about taking out a policy. He recognized the dead man at once. Quarles was not even right as regards the verdict. The doctor's evidence suggested that there were certain signs of a struggle which one would not expect to find in a deliberate suicide, but which were natural if a man tried to save himself from drowning. This, and there being no reason why Dr. Smith should have taken his own life, and the conviction of his wife and his assistant that he was not the kind of man to do such a thing, so impressed the jury that they returned a verdict of accidental death by drowning. Here would have been an end of the case had not the insurance company raised difficulties and made all sorts of excuses to delay the payment of the money. Criticism was aroused; letters appeared in the papers. The company stated that they were acting on the advice of their solicitors, and then someone suggested that solicitors of such standing as the firm mentioned would hardly persevere in such advice unless the police authorities were behind them. So police methods were criticized by all kinds of people anxious to rush into print, and since I was the immediate cause of the trouble, acting on Christopher Quarles's advice, I grew a little anxious. Mrs. Smith had come to London and was staying at a boarding house in Bloomsbury, a most injured woman by common consent. From the moment she had left Riversmouth I had had her watched, and nothing had happened. Why had I set a spy upon her movements? Because I had listened to Quarles in that empty room at Chelsea. Two days after the inquest I went to see the professor. He had read the account in the papers. "You see it was not 'Found drowned,'" I said.