"Good," he exclaimed under his breath. "If I put a lot of black marks on his back it will not only destroy his power, but everyone who sees them will know that he is a villain. I know that black marks were what teachers used to give us to show that our deportment wasn't good," and in a jiffy Billy had covered Nickel Plate's back with black marks.
Poor Nickel Plate had no idea what was going on behind his back; indeed he was so surprised at the Coal Man's antics that he couldn't think of anything else. For, of course, the Coal Man saw what Billy was doing, and was laughing and slapping his knees and jumping up and down with delight.
"Well, come on Drone," said Nickel Plate, starting away. "We must be going—Drone—Drone—wake up, I say."
And Drone got up from a bed of lava rubbing his eyes and yawning. But he was so sleepy he paid no attention to Nickel Plate's back and out they both walked without ever discovering the trick Billy had played.
As soon as they had gone Billy came out of his hiding-place.
"Thank you, Mr. Coal Man, Mr. Alchemist, and Ace of Spades—I shan't ever forget your kindness to me."
"Run along and don't interrupt," said the Alchemist, hard at work with his scales. "You're welcome—good-by."
Ace of Spades bobbed his red head and smiled to show that Billy was welcome to all he had done.
"Come along," said the Coal Man, "I'll show you the way out." And he led Billy to the floor beneath the Crater where he warmly shook hands with him. "Good-by—take good care of yourself, boy—you've made me laugh more to-day than I have for years."