That afternoon, accompanied by Inspector Carfon, Malcolm Sage motored down to "The Hollows," which lies at the easternmost end of the village of Gorling. The inspector stopped the car just as it entered the drive. The two men alighted and, turning sharply to the right, walked across the lawn towards an ugly red-brick building, screened from the house by a belt of trees. Malcolm Sage had expressed a wish to see the laboratory first. It was a strange-looking structure, some fifty feet long by about twenty feet wide, with a door on the further side. In the red-brick wall nearer the house there was nothing to break the monotony except the small wicket through which the professor's meals were passed. Malcolm Sage twice walked deliberately round the building. In the meantime the inspector had removed the seal from the padlock and opened the door. "Did you photograph the position of the body?" enquired Malcolm Sage, as they entered. "I hadn't a photographer handy," said the inspector apologetically, as he closed the door behind him; "but I managed to get a man to photograph the wound." "Put yourself in the position of the body," said Malcolm Sage. The inspector walked to the centre of the room, near a highly-polished table, dropped on to the floor and, after a moment's pause, turned and lay on his left side, with right arm outstretched. From just inside the door Malcolm Sage looked about him. At the left extremity a second door gave access to another apartment, which the professor used as a bedroom. A little to the right of the door, on the opposite side, stood the fireplace. This was full of ashes, apparently the charred remains of a quantity of paper that had been burnt. On the hearth were several partially-charred envelopes, and the paper-basket contained a number of torn-up letters. "That will do, Carfon," said Malcolm Sage, as he walked over to the fireplace and, dropping on one knee, carefully examined the ashes, touching them here and there with the poker. He picked up something that glittered and held it out to the inspector who scrambled to his feet, and stood looking down with keen professional interest. "Piece of a test tube," remarked Malcolm Sage, as he placed the small piece of glass upon the table. "Moses' aunt!" gasped the inspector. "I missed that, though I saw a lot of bits of glass. I thought it was an electric bulb." "Somebody had ground it to powder with his heel, all except this piece. Looks as if there might have been more than one," he added more to himself than to the inspector. "These are not letters," he continued without looking up. "Not letters?" "The paper is all of the same quality. By the way, has anyone disturbed it?" He indicated the grate. "No one," was the reply. Malcolm Sage rose to his feet. For some minutes he stood looking down at the fireplace, stroking the back of his head, deep in thought.