"This is really a most remarkable mystery, Urwin," he exclaimed at length, twisting the plain gold ring upon his finger, a habit of his when pondering deeply. "There seem a thousand complications. It's absolutely the most astounding case that I've ever had in hand. Even Shaw, our superintendent at the Yard, a man whose deep-rooted conviction is that we never need fail if we really take an interest in an inquiry, acknowledged to me the other day that he could see no way to a clue. Of course, we might question Mrs. Blain, or even arrest Blain himself on suspicion if we could find him again. But whoever is guilty has taken such careful precautions to obliterate every trace of a clue that both the superintendent and myself are agreed that the interrogation of either of the Blains would only result in defeating our ends." That was exactly my own opinion. I had many times wondered why the police had not made inquiries of Mrs. Blain on account of the statement by the landlord at Kensington, but it was now plain that the Director of Criminal Investigations, the greyheaded, loud-voiced, old gentleman whom I knew quite well at Scotland Yard, had decided otherwise. "But why are you so anxious that my friend Cleugh should remain in ignorance of our movements?" I inquired. "You say that he loves Mary Blain," answered Boyd. "He might in that case drop some unintentional hint to her of the direction of our inquiries. This matter, to be successful, must be entirely a secret between ourselves--you understand? To-day we've made a discovery--the identity of the man who threw some object into the lake--and it puts a rather fresh complexion upon the affair, even though it further complicates it considerably. You said that his wife has all along told you that her husband was in Paris--I think?" "Yes," I responded. "She said he was there in connexion with some company which he was trying to promote." "And all along he has been in London--in hiding." "He may have just returned from Paris," I suggested. "Recollect that I've not been to Riverdene for some little time." "No, my dear fellow," Boyd said. "His ingenuity in eluding us in Ebury Street showed that he had already prepared a snug hiding-place for himself before that tragedy at Phillimore Place. Besides, the other evening his clothes showed an attempt at disguise--didn't they?" "Certainly. He's very smartly dressed always; indeed, rather a fop in his way." "Depend upon it that he's never dared to set foot outside London all this time. He knows well enough that the Metropolis is the safest place in the whole world in which a criminal may conceal himself. Only a bungler attempts to get away abroad." Silence again fell between us. The quiet was unbroken save for the slow ticking of the clock upon the mantelshelf. Of a sudden, with a rather curious glance, he bent forward to me, eagerly saying--