Shortly after daybreak that morning, Bill Bolton spiralled his small two-seater down to a crosswind landing on a field back of Pawling, New York. The monoplane bumped onward over the rough stubble for a few yards and stopped.

Bill stripped off his headphone and turning in his seat, faced toward Osceola and Ashton Sanborn who were wedged into the rear cockpit. The field, though comparatively level, was high on the mountain side. From where he sat he had a lovely view of a wide valley and a village nestling amid the trees near the base of the mountain. But Bill ignored the view. He seemed rather put out this morning.
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“Well, here we are,” he announced grumpily. “I hope you’re pleased. Orders are orders, but if you ask me, Mr. Sanborn, I think it’s the bunk.”

The two aft got out of the cockpit and Sanborn walked forward to Bill who was glaring at the instrument board.

“Sorry, old man,” the detective held out his hand. “Won’t you wish me luck?”

Bill turned his head quickly and smiled at his friend. “Of course I will, Mr. Sanborn,” his tones carried sincerity. “Here’s the best of luck to you, and a full bag!”

They shook hands. “I know,” said Sanborn, “that both you and Osceola feel badly about this. But you two fellows constitute our rear guard—and believe me when I say that you’re undertaking a very grave responsibility.”
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Osceola came up and laid an affectionate hand on the older man’s shoulder. “Good hunting, boss. Neither Bill nor I are ever quite ourselves so early in the morning, and especially so after a heavy night.”

“Oh, I know I’m a grouch today.” Bill laughed, though not very convincingly. “But it’s a disappointment, after what we three have been through on this business, not to be in at the finish. Don’t apologize for me, Osceola. I know I’m acting like a spoiled kid—I’ll get over it after a while.”

“If the Professor spots my men and Captain Simmonds’ police,” said Sanborn, “his plane won’t land. Then it is up to you fellows to get after him, and I give you carte blanche—you can do as you like about it.”

“Force down the Fokker and capture the villain,” said Osceola. “If we can.”

“That’s the idea,” replied Sanborn cheerfully.
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“Only,” said Bill, “Professor Fanely won’t spot the secret service men and the police because they’ll be too well hidden. All that you and I will get out of it, Osceola, is a rotten view of the battle, half a mile away, from those trees over yonder. It’s a grand life, this secret service stuff—if you like it!”

“I’ll tell you one thing, Bill,” promised the detective, “if this raid is pulled off successfully, and we round up the cartwheel gang in their lair, the people of the United States will have you to thank for saving them from the most frightful menace that has ever threatened this land of ours. And I’ll see that you get full credit.”

Bill leaned over the side of the cockpit. “Why, that’s the bunk, too, Mr. Sanborn—and you know it. Osceola found the first winged cartwheel and—”

“And ran it to a dead end,” supplied the chief calmly. “You were the brains of this piece, Bill.”

“And you also put in plenty of grit and brawn,” amended the secret service man.

“Heck, no. How about yourself, Mr. Sanborn? You’ve been running the show.”
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“But if you hadn’t saved my life last night, Bill, my boy, I wouldn’t be running anything. And as the Chief says, without your brains, the winged cartwheels mystery would have remained unsolved—and I would still be watching poor Kolinski, over at Heartfield’s. No, Bill, you’ve played the lead in this piece, there’s no disputing it.”

Bill grinned and shook his head. “Sorry I can’t agree with you.” He leaned back in his seat and twiddled the stick. “Here comes Captain Simmonds. I reckon it’s time you and I, Osceola, pushed this bus into the shade of those trees. No need to give any more publicity than we have to, to our whereabouts.”

The State Police Captain strode across the field. “Morning, everybody. The men are posted, Mr. Sanborn. We’ve got the Mizzentop hotel completely surrounded. When Fanely arrives we’ll rush the plane and the house at the same time.”
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“You won’t, unless you hurry—” Osceola’s sharp ears had detected a distant hum in the air to the southeast, “here comes the Fokker now!”

Simmonds uttered an exclamation of fury.

“Tarbell is in charge. He’ll handle things all right.” Sanborn though seriously disturbed, was outwardly calm. “Stupid of us not to expect Fanely earlier. But you and I had better hop it, Captain.”

The big airplane appeared suddenly over the top of the mountain; then, just as suddenly went into a steep right bank.

“Wait!” Bill snapped out the order. “They’ve seen us! Swing this bus into the wind. If that Fokker gets away now, we’ll have it to do all over again.”
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The three on the ground grasped the situation instantly. They took hold of the tailplane and slewed it round in a quarter circle, as Bill switched on the ignition. Almost immediately, the inertia starter set the propeller revolving, and Osceola taking a running leap half vaulted, half climbed into the rear cockpit. They were moving slowly over the rough ground now, the engine roaring.

With his feet on the rudder pedals and right hand on the stick, Bill adjusted helmet and goggles as the engine warmed up. Then he cut down the throttle speed and clapped on his phone set. A twist of the head told him that Osceola was secure, and he roared the engine into twelve hundred revolutions per minute. They were rolling in earnest now. Bill lifted his ship off the ground with the engine beating a steady tattoo. Then he opened her up wide and pulled back on the stick.
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They climbed steadily, heading after the Fokker, which now was but a dot to the southward, and bucking a twenty mile wind from the sea. The air was slightly bumpy, and sharp knocks on the bottom of their fuselage gave the impression of rolling over cobble-stones. Far above the roaring plane, little clouds, like balls of fluff, swam in the light ether.

At fifteen hundred feet, the approximate altitude of the Fokker, Bill leveled o............