For a second or two Harry stared. But he knew there could be no snake as broad as this crawling figure appeared to be. "Who's there?" Hazelton called quickly. The writhing mass became still, flattening itself against the bed of rock. Hazelton was not to be deceived, however. "Who's there?" Harry repeated. "You had better talk up, my man!" Still no sound. Harry started forward to investigate. His foot touched against a good sized fragment of rock left there by one of the masons. Without delay Harry reached down, picking up the rock, which was rather more than half as large as his head. Holding this in his right hand Harry advanced with still more confidence, for he felt himself to be armed. Hazelton had been a clever pitcher in his high school days and knew that he could make this fragment of rock land pretty close to where he wanted it to go. "Who are you?" demanded Hazelton, once more, as he stepped cautiously forward. "No use in your keeping silent, my man. I see you and know that you're there. Moreover, I'm going to drag the truth out of you as to what you're doing out here on the wall at this hour of the night---and to-night of all nights." Still no answer; Harry went steadily forward, until he was within a dozen feet of the head of the flattened brute in human guise. Hazelton could now see every line of his adversary plainly, though he could not make out the fellow's face. "You'd better get up and talk," warned Harry, poising the rock fragment for a throw. "If you don't you'll cast all the more suspicion upon yourself. For the last time, my man, who are you and what are you doing here?" The huge black figure might have been a log for all the answer that came forth. "All right, then; it's your own fault," Harry Hazelton continued calmly. "As you won't speak I'm going to crack the nut for myself. Your head will be the nut, and this rock I have in my hand shall be the hammer. I'm going to slam this rock on your head with all the force I've got, and I'm a good, straight thrower." Yet, though Hazelton spoke with such confidence, he was far from meaning all he said. In the first place, he had no legal right, under the circumstances, to go as close to murder as it might be for him to throw the rock at the rascal's head. Moreover, Harry would hardly have exercised such a legal right, had he possessed it, without the strongest provocation. From the black prowler came a sudden, fierce snort. It sounded altogether like defiance. "Ho---ho! You're finding your voice, are you, my man?" Hazelton jeered. "Then talk up in time to save yourself!" Instead the huge black man began to writhe forward. "Stop that!" ordered Harry dangerously. He did not retreat from the writhing human thing, but he took better aim, noting that the black man was hatless and that his head offered a fair mark. "You're going to get hurt in just about a second more," he added.