Hewitt followed the girl to the basement, apparently looking straight before him, but in reality taking in every detail of the place. The gas meter was in a very large lumber cupboard under the kitchen stairs. The girl opened the door and lit a candle. The meter stood on the floor, which was littered with hampers and boxes and odd sheets of brown paper. But a thing that at once arrested Hewitt's attention was a garment of some sort of bright blue cloth, with large brass buttons, which was lying in a tumbled heap in a corner, and appeared to be the only thing in the place that was not covered with dust. Nevertheless, Hewitt took no apparent notice of it, but stooped down and solemnly tapped the meter three times with his pencil, and listened with great gravity, placing his ear to the top. Then he shook his head and tapped again. At length he said:-- "It's a bit doubtful. I'll just get you to light the gas in the kitchen a moment. Keep your hand to the burner, and when I call out shut it off _at once_; see?" The girl turned and entered the kitchen, and Hewitt immediately seized the blue coat--for a coat it was. It had a dull red piping in the seams, and was of the swallow-tail pattern--a livery coat, in fact. He held it for a moment before him, examining its pattern and colour, and then rolled it up and flung it again into the corner. "Right!" he called to the servant. "Shut off!" The girl emerged from the kitchen as he left the cupboard. "Well," she asked, "are you satisfied now?" "Quite satisfied, thank you," Hewitt replied. "Is it all right?" she continued, jerking her hand toward the cupboard. "Well, no, it isn't; there's something wrong there, and I'm glad I came. You can tell Mr. Merston, if you like, that I expect his gas bill will be a good deal less next quarter." And there was a suspicion of a chuckle in Hewitt's voice as he crossed the hall to leave. For a gas inspector is pleased when he finds at length what he has been searching for. Things had fallen out better than Hewitt had dared to expect. He saw the key of the whole mystery in that blue coat; for it was the uniform coat of the hall porters at one of the banks that he had visited in the morning, though which one he could not for the moment remember. He entered the nearest post-office and despatched a telegram to Plummer, giving certain directions and asking the inspector to meet him; then he hailed the first available cab and hurried toward the City.