Somehow the problem, when I had once stated it to myself and had taken it for ever out of that dim region of intangible speculation, did not surprise me very greatly. Instinctively I recalled how significant had been the Spaniard's appeal to the colonel when he threatened to compel Doris to hold no further communication with me. "I beg you withdraw that, withdraw it this day, or you will regret your determination." Then I saw again Don Jose as he had looked when he knelt, just where I was sitting at that moment, with the sullen glare of the flames on his upturned face and his dagger poised to catch the light on the edge that he had just finished sharpening with so much intensity and precision. After all, it was quite possible that the lust of murder had seized him in those seconds, the desire to make good his own words both to the colonel and to myself. It would appear so easy to commit a crime when all London slept; and, alas! it had been easy, painfully, pitilessly easy, to put an end to that gallant old soldier as he lay slumbering in his bed. Certainly one great damning fact stood out against Casteno-- the killing of the colonel's dog Fate. Who else could have any interest in the stabbing of that poor, faithful brute than the murderer of his master? And who else could have made that ugly gash in his side save Jose Casteno? Nor, indeed, was that the only solid link in the chain of guilt I was forging against the Spaniard. All at once I recalled how carefully he had avoided the passage where the spaniel had been stricken down. Was that accident--or conscience? Also the agility he had shown in scrambling up that iron pipe outside the hunchback's shop when we went to spy on Zouche from that upstairs room. He had told me, of course, he had learned the trick at sea. He may have done that; but might he not also have acquired some recent practice outside Embankment Mansions which it seemed pretty clear the murderer entered by the same method? Stung to desperation at my own foul success in linking my employer up with this awful crime I resolved that I would lose no time in tracking the man down, and his guilt. What did the Lake of Sacred Treasure in far-off Mexico matter to me in an hour red with blood as that was--the blood of one of my best and truest friends? Let the Earl of Fotheringay and Lord Cyril Cuthbertson plot and plan. Let Mr Cooper-Nassington ferret out Peter Zouche and drag from him the secret of the cipher manuscripts. Ay, let the Jesuits send their most trusty spies, I at least would take no hand in the struggle again until I had torn the mask from this villain.