"Quite," Dashwood muttered. "Most amazing. We did not go to bed till very late, which makes it all the more remarkable. It must have been practically daylight before the miscreant could have begun to work." "It certainly is a novelty," the Inspector replied, "but I want to convince you fully that I am right in my conclusion. You will see that parts of the ashes, very minute parts, are plastered together as if they were wet. Also you will see that the floor has been burnt in a kind of channel nearly as far as the door. It is only a narrow channel, but at the same time it is perfectly well defined. Now, what caused the floor to burn in that erratic manner? I am going to tell you. Let us follow that track up as far as the door. There is a large stone with little cracks at the side into which a liquid of some kind has fallen or run rather." The speaker bent down and rolled a scrap of paper into the moisture which lay shining in the crack of the stone. Then he handed the paper to Sir George. "Will you kindly smell that, sir," he asked, "and tell me what you make of it?" "No trouble at all about that," Dashwood exclaimed; "the stuff is paraffin beyond a doubt." "Precisely. The straw was dumped on the floor and then saturated with paraffin. If the straw was slightly damp, that would account for the dense quantity of smoke. The paraffin ran into little ripples over the floor, which accounts for the strange track of the flames. But we can ascertain that to a certainty." A question or two being asked, it was discovered that a large can of petroleum was missing from one of the toolsheds. A little later the empty tin was discovered in one of the flower-beds. The discussion was at its height when Mary appeared. She looked very pale and shaky, otherwise she maintained her self-possession. But as she listened to the strange story it seemed to Ralph Darnley that she was disturbed about something. The pallor of her face became more marked, her eyes filled with something like fear. Did the girl know anything about it, Ralph asked himself? If not, why did she appear to be so strangely moved by the plain recital? The thought was ignoble and unworthy, but Ralph could not free himself from it altogether. He drew Mary a little apart from the rest; he could see that she was trembling with some strong emotion. "The old house has had a very narrow escape," he began. "All Horace Mayfield's carefully prepared plans were very nearly in vain. If the house had been destroyed----" "I--I did not look at it in that light," Mary stammered. "As you say, nothing could have mattered had the house perished. Where are those men now?"