"Positive. I read about these bombs recently. A German invented them to be used in attacking a besieged city in case of war."
"But how did this one get on my shed roof?" asked Tom.
"It was dropped there by the mysterious airship!" exclaimed the odd man. "That was why the aeroplane moved about over your place. Those in it hoped that the fire would not break out until you were all asleep, and that the shed and the Humming-Bird would be destroyed before you came to the rescue. Some of your enemies are still after you, Tom."
"And it was Andy Foger, I'll wager!" he cried. "He was in that aircraft! Oh, I'll have a long score to settle with him!"
"Of course you can't be sure it was he," said Mr. Damon, "but I wouldn't be a bit surprised but what it was. Andy is capable of such a thing. He wanted to prevent you from taking part in the race."
"Well, he sha'n't!" cried Tom, and then he thought of his invalid father. They made a further examination of the shed, and discovered another empty bomb. Then Tom recalled having seen something drop from the mysterious aeroplane as it passed over the shed.
"It was these bombs," he said. "We certainly had a narrow escape! Oh, wait until I settle my score with Andy Foger!"
As there would be but little use for the aeroplane shed now, if Tom sent his craft off to the meet, it was decided to repair it temporarily only, until he returned.
Accordingly, a big tarpaulin was fastened over the hole in the roof. Then Tom put a new wing tip on in place of the one that had been scorched. He looked all over his sky racer, and decided that it was in fit condition for the coming meet.
"I'll begin to take it apart for shipment, as soon as I hear from the specialist that dad is well enough for me to go," he said.