"You are a fool," was the stinging remark he heard flung at him. "Do you want to play the police-officer here and arrest me in mid air?"

"Mr. Brotherson, you understand me as little as I am supposed to understand you. Humble as my place is in society and, I may add, in the Department whose interests I serve, there are in me two men. One you know passably well - the detective whose methods, only indifferently clever show that he has very much to learn. Of the other - the workman acquainted with hammer and saw, but with some knowledge too of higher mathematics and the principles upon which great mechanical inventions depend, you know little, and must imagine much. I was playing the gawky when I helped you in the old house in Brooklyn. I was interested in your air-ship - Oh, I recognised it for what it was, notwithstanding its oddity and lack of ostensible means for flying - but I was not caught in the whirl of its idea; the idea by which you doubtless expect, and with very good reason too, to revolutionise the science of aviation. But since then I've been thinking it over, and am so filled with your own hopes that either I must have a hand in the finishing and sailing of the one you have yourself constructed, or go to work myself on the hints you have unconsciously given me, and make a car of my own."

Audacity often succeeds where subtlier means fail. Orlando, with a curious twist of his strong lip, took hold of the detective's arm and drew him in, shutting and locking the door carefully behind him.

"Now," said he, "you shall tell me what you think you have discovered, to make any ideas of your own available in the manufacture of a superior self-propelling air-ship."

Sweetwater who had been so violently wheeled about in entering that he stood with his back to the curtain concealing the car, answered without hesitation.

"You have a device, entirely new so far as I can judge, by which this car can leap at once into space, hold its own in any direction, and alight again upon any given spot without shock to the machine or danger to the people controlling it."

"Yes. It's a brilliant idea; I could never have conceived it."

"Sit here. Let's see what you know."