"Somebody crept into his bedroom as the colonel slept and stabbed him to the heart--to be precise, the exact hour you left me to search for Paul." "Good heavens!" gasped Casteno, falling back. "Then the wretched boy has broken loose from his reason and carried out his insane idea of revenge! Ah! now I see it all. That was why I caught him lurking about your office! He had tracked Colonel Napier there earlier, and had no notion that he had returned to Whitehall Court until he saw a strange figure at your door." "Even that doesn't explain who killed the clumber spaniel Fate." "I think it does," urged Casteno stoutly. "The dog knew, somehow, he had done wrong to his master and would not leave him. In a fit of passion and terror Paul whipped out his knife and stabbed him." "But that would happen near Whitehall Court. How came the dog to die in a passage near Stanton Street?" "He must have been making for your office: remember all dogs have odd gleams of foresight at times." For a few moments we walked on in silence. The duel had been a sharp one and a long one, but already I was possessed with an uncomfortable suspicion that the Spaniard had won. Even as I surveyed the ruins of my theories I was conscious that little was left to connect Casteno with the murder. "But do you think your brother Paul will be discovered?" I asked. "I cannot tell," said Casteno, and I could see now he was sincerely grieved at the disastrous intelligence I had communicated to him. "There are sure to be plenty of people in Embankment Mansions who will remember the caning which the lad had from the colonel on the stairs. They will be certain, when they recover their wits, to give the police the details of that affray; also there is that discharged servant I spoke of--the man Butterworth. He hates Paul like poison. He will leave no stone unturned, I am certain, to connect the lad with the crime. "Still, mere suspicion is one thing, and evidence strong enough to warrant arrest is another," he added after a moment's careful consideration. "Perhaps, after all, I am wrong. Somebody else may have done it. We shall see." "Whoever it is I shall do my best to bring them to justice," I cried hotly. "I don't care whether it is Paul Zouche--" "Of course not," replied Casteno with much dignity. "I have no doubt you will communicate all I have repeated to you to Scotland Yard. Indeed, I never had any two opinions on that score. At the same time you must excuse me if I don't evince any keen desire to debate the matter further." "I never asked you to do so," I retorted, anxious not to be outdone in courtesy by the Spaniard. "All your statements to me were practically volunteered." "True," said Casteno. "As a matter of fact, I felt they were honestly due to you. I saw that my absence from your rooms at the time when the colonel was murdered looked very ugly for me. Very ugly, indeed."