“But he inspected the machine every time he flew. He walked around it and checked mounts and stays and everything. Just like all of us do. So did his mechanicians, just like you do for me.”

“Could have hit a rock bouncing on the field.”

“He would have noticed, felt it, heard it.”

“He’d notice if it shattered the propeller,” said Andy. “But if a rock hit right on the hub at the same moment he had his hands full just getting her into the air and his motor was straining loudly, maybe he didn’t. Couple of months ago I heard about a propeller getting unstable because it was stored standing up. Moisture sunk into the bottom blade.”

“His was brand-new and used nearly every day since he got it.”

“Yeah, but you get these cracks.”

“That’s why it was painted silver,” countered Bell, “so little cracks would show.” That was standard procedure on pushers. His own propeller was not because a silver propeller spinning in front of the driver would dazzle him.

“I know, Mr. Bell. And obviously it wasn’t around long enough to rot, either.” Moser looked up at the tall detective. “If you’re asking me was it sabotage, I’d say it sure as heck could have been.”

“How? If you wanted a fellow’s propeller to fly off, what would you do?”

“Anything I could to throw it out of kilter. When the propeller is off balance, it vibrates. Vibrations will break it or rattle the hub loose, or even shake the motor right off its mounts.”

“But you wouldn’t want it shaking that much because the fellow you’re trying kill would notice and stop his motor and volplane down as fast as he could.”

“You’re right about that,” Andy said gravely. “The saboteur would have to really know his business.”

But that, Isaac Bell had to admit, was true of every mechanician in the race, with the possible exceptions of Josephine’s disguised detectives. Another truth he could not ignore was that Preston Whiteway had gotten the wish he had so unabashedly hoped for back in San Francisco. He had had to wait long past Chicago and halfway across Kansas, but a “winnowing of the field” had indeed turned the race into a contest that pitted the best airmen against plucky tomboy Josephine.

Eddison-Sydney-Martin had probably been the best—and his winnowing by sabotage had hardly been natural. But steady Joe Mudd was proving himself to be no slouch, while the thoroughly unpleasant but undeniably courageous Steve Stevens was a fast flier who pushed ahead unintimidated by the vibrations endangering his machine.

Bell had no way of knowing who the saboteur would try to attack next. In fact, the only thing that the tall detective knew absolutely for sure was that his first job was still what it had always been: keep Harry Frost from killing Josephine.