up—there was a narrow stone passage—steps that went down a door with a light under it. It was, somehow, difficult to put out one's hand to that door and open it.
"Nonsense!" Gerald told himself, "don't be an ass! Are you invisible, or aren't you?"
Then he opened the door, and someone inside said something in a sudden rough growl.
Gerald stood back, flattened against the wall, as a man sprang to the doorway and flashed a lantern into the passage.
"All right," said the man, with almost a sob of relief. "It was only the door swung open, it's that heavy—that's all."
"Blow the door!" said another growling voice; "blessed if I didn't think it was a fair cop that time."
They closed the door again. Gerald did not mind. In fact, he rather preferred that it should be so. He didn't like the look of those men. There was an air of threat about them. In their presence even invisibility seemed too thin a disguise. And Gerald had seen as much as he wanted to see. He had seen that he had been right about the gang. By wonderful luck—beginner's luck, a card-player would have told him—he had discovered a burglary on the very first night of his detective career. The men were taking silver out of two great chests, wrapping it in rags, and packing it in baize sacks. The door of the room was of iron six inches thick. It was, in fact, the strong-room, and these men had picked the lock. The tools they had done it
