Tom’s monoplane was making no more noise, now, than a soaring bird.  He was gliding swiftly toward the earth, and, with the plan in his mind of administering some sort of punishment to the bully, he aimed the machine directly at him.

Nearer and nearer shot the monoplane, as quietly as a sheet of paper might fall.  Andy pedaled on, never looking up nor behind him, A moment later, as Tom threw up his headplanes, to make his landing more easy, and just as he swooped down at one side of the cyclist, our hero let out a most alarming yell, right into Andy’s ear.

“Now I’ve got you!” he shouted.  “I’ll teach you to slash my aeroplane!  Come with me!”

Andy gave one look at the white bird-like apparatus that had flown up beside him so noiselessly, and, being too frightened to recognize Tom’s voice, must have thought that he had been overtaken by some supernatural visitor.

Andy gave a yell like an Indian, about to do a stage scalping act, and fairly dived over the handlebars of his bicycle, sprawling in a heap on the dusty road.

“I guess that will hold you for a while,” observed Tom, grimly, as he put on the ground-brake and brought his monoplane to a stop not far from the fallen rider.

CHAPTER V—­A MYSTERIOUS MAN

For several minutes Andy Foger did not arise.  He remained prostrate in the dust, and Tom, observing him, thought perhaps the bully might have been seriously injured.  But, a little later, Andy cautiously raised his head, and inquired in a frightened voice: 

“Is it—­is it gone?”

“Is what gone?” asked Tom, grimly.

At the sound of his voice, Andy looked up.  “Was that you, Tom Swift?” he demanded.  “Did you knock me off my wheel?”

“My monoplane and I together did,” was the reply; “or, rather, we didn’t.  It was the nervous reaction caused by your fright, and the knowledge that you had done wrong, that made you jump over the handlebars.  That’s the scientific explanation.”

“You—­you did it!” stammered Andy, getting to his feet.  He wasn’t hurt much, Tom thought.

“Have it your own way,” resumed our hero.  “Did you think it was a hob-goblin in a chariot of fire after you, Andy?”

“Huh!  Never mind what I thought!  I’ll have you arrested for this!”

“Will you?  Delighted, as the boys say.  Hop in my airship and I’ll take you right into town.  And when I get you there I’ll make a charge of malicious mischief against you, for breaking the propeller of the Butterfly and slashing her wings.  I’ve mended her up, however, so she goes better than ever, and I can take you to the police station in jig time.  Want to come, Andy?”

This was too much for the bully.  He knew that Tom would have a clear case against him, and he did not dare answer.  Instead he shuffled over to where his wheel lay, picked it up, and rode slowly off.