“In order to qualify for your pilot’s license, Mr. Bell, you are required to ascend to one hundred feet and fly around the pylon-marked course. Then you will ascend to five hundred feet and remain there ten minutes. Then you will demonstrate three methods of descent: a safe volplane in a series of circles, a gradual ocean-wave downward coast, and a sharper spiral dip. Is that clear?”

Bell grinned. “Is it O.K. if I keep moving while remaining at five hundred feet for ten minutes?”

“Of course. You have to keep moving. Otherwise, the machine will fall. Off you go! I haven’t all day.”

But no sooner had Bell’s motor blatted to noisy life than the rotund Grady Forrer, Van Dorn’s head of Research, galloped through the castor oil smoke, shouting for Isaac to wait.

Bell held down his blip switch. The Gnome sputtered to a grudging stop. Andy Moser brought the soapbox used to climb up to the monoplane. Grady heaved himself on it, saying, “Found out how Frost survived getting shot by you and Archie.”

“Well done! How?”

“Remember I told you that ten years ago a Chicago priest manufactured a so-called bulletproof vest of multiple layers of a particularly tight silk cloth specially woven in Austria?”

“But the Army rejected it. It weighed forty pounds and was hot as Hades.”

“Guess who invested in their manufacture anyway?”

“Chicago,” said Bell. “Of course. Exactly the sort of thing Harry Frost would have gotten a line on and seen its potential. To be bulletproof is a criminal’s dream.”

“And a fellow his size could carry that weight.”

“So the only wound Harry Frost suffered was the jaw Archie broke as he went down.”

“Next time,” said Grady Forrer, “bring a cannon.”

Bell ordered Grady to pass the word to every man on the case. Sidearms—knives, revolvers, and automatics—would not pierce it. Bring rifles. And shoot for the head, just to be on the safe side.

“All right, sir,” he called to the Aero Club certifier. “I’m ready for my test.”

Andy reached to spin the propeller. Bell touched his blip switch. About to shout, “Contact!” he said instead, “Wait!”

“Now what?” exclaimed the Aero Club official.

From the corner of his eye, Bell saw running toward him a hideously scarred young Van Dorn agent from the New York office. Bell signaled Andy, who was reaching to spin the propeller. Andy replaced the wooden soapbox. Eddie Tobin jumped on it and leaned in close so only Bell could hear.

“Looks like they spotted Harry Frost at Saint George.”

St. George, on Staten Island, was a resort town where the Kill Van Kull met the Upper Bay. It was home to grand hotels with beautiful views of New York’s harbor. The busy waterfront served ferries, tugs, coal barges, steam yachts, fishing boats, and oyster scows.

“How sure are you it was Frost?”