"Because it is a piece of umbrella silk. The murderer was carrying an umbrella--and an open umbrella--have you the piece of silk? If so, let us look at it." The superintendent produced the square inch of silk from his waistcoat pocket, and examined it closely: "Of course it's umbrella silk," he exclaimed, slapping his leg. "Funny I didn't recognise it at the time." "Perhaps I wouldn't have recognised it myself, but for the fact that a piece of umbrella silk formed an important clue in a recent case I was engaged upon," replied the detective. "Experience counts for a lot--sometimes. See, this piece of silk is hemmed on the edge--pretty conclusive proof that the murderer was carrying the umbrella open, to shield him from the rain, and that it caught on the nail outside the window, tearing off the edge. He closed it as he got inside the window, and placed it near the window-sill, and the rain dripped off it and formed the pool of water. The size of the pool, and the fact that the murderer carried an open umbrella to shield him, prove pretty conclusively that he made his entrance into the room during the time the rain was falling heaviest--which was between 11.10 p.m. and 11.30. "We now come to what is the most important discovery of all--the pieces of candle-grease we found in the murdered man's bedroom. They help to establish two curious facts, the least important of which is that somebody tried to light the gas in Mr. Glenthorpe's room last night, and, failing to do so, went downstairs and turned on the gas at the meter." "What if they did?" grunted Superintendent Galloway, pouring out another glass of brandy. He was secretly annoyed at having overlooked the clue of the umbrella silk, and was human enough to be angry with the detective for opening his eyes to the fact. "I don't see how you're going to prove it, and, even if you did, it doesn't matter a dump one way or the other." "We'll let that point go," rejoined Colwyn curtly. "Your attitude in shutting your eyes to facts hardly encourages me to proceed, but I'll try. Would you mind showing me those bits of candle-grease you picked up in the bedroom?" Superintendent Galloway produced a metal match-box from his pocket, emptied some pieces of candle-grease, a burnt wooden match and a broken matchhead from it, and sat back eyeing the detective with a supercilious smile. Colwyn, after examining them closely, brought from his own pocket an envelope, and shook several more pieces of candle-grease on the table. "Look at these pieces of candle-grease side by side," he said. "Yours were picked up alongside the bed; I found mine underneath the gas burner." Superintendent Galloway glanced at the pieces of candle-grease with the same supercilious smile. "I see them," he said. "They are pieces of candle-grease. What of them?"