"But he was around our workshop just before we made this last
flight!" insisted Jack. "He came in pretending he had left some of
his important drawings behind when he went away, but I noticed that
he hung around the airship a good bit. I saw him looking at, and
running the gyroscope, and I'm sure he did something to it that
caused it to fail to work, and so wrecked us."

"You should not say such things," chided Mr. Vardon.

"Well, I believe it's true," insisted Jack. "And you found
something wrong with the gyroscope, when you took it from the
airship; didn't you?"

"Yes, but that may have occurred in the wreck."

"No, that gyroscope began to act wrong before we started to fall,"
went on the helper. "I noticed it, and I believe that mean
lieutenant monkeyed with it. He wanted you to think your plans were
failures."

"I should dislike to believe that of anyone," spoke Mr. Vardon,
seriously.

"Well, I'm going to keep my eye on him," said Jack. "He won't get
another chance at any of our machines."

It was a day or so after this conversation that Dick came upon his
chum Innis, talking to Mr. Vardon. They seemed very much in
earnest, and at Dick's approach the aviator strolled away. Innis
stood regarding him a moment, and remarked, in a low tone: