Suddenly the crash of the motor ceased and Nukharin banked the ship up in a spiral glide. Quest had never been in the air before, and the long whirl down into the darkness on this devil's errand was to him as eery as a ride to perdition in a white-hot projectile. His mind seemed to trail out in a great nebular helix behind the descending ship. He felt that he had suddenly crossed some cosmic meridian into a new plane of existence, where he was changed to a gas, yet continued capable of thought. But even here his obsession remained the same. Keane Clason--trickster, traitor, arch-criminal--must be destroyed! "I'll get him!" vowed Quest in words that were no less real for being soundless. "I'll trail him to the end of space and bring him to account!" * * * * * Then wheels touched earth and the cold, bare facts of his destiny rushed in on him with redoubled force. He felt the nearness of his Control seconds before he perceived him through the eyes of Philip. With a sensation like a stab he realized that now he must speak, play his part, be any bloodless hypocrite that Keane Clason chose to make him. The silent order surged down the conduits promptly enough; he responded as an automaton obeys the pressure of a button. "Well, Doctor," chuckled Philip with a cunning leer, "here's the magic tower, just as I promised you. We'll run it up in a jiffy. This test is going to be so vivid and conclusive that not even a hard-headed skeptic like you can raise a question." "You misunderstand me," returned Nukharin in an injured tone. "So far as I am concerned this procedure is only a formality, but it is none the less necessary. Suppose that I should spend a hundred million of my government's money and the purchase prove worthless? You may guess that my folly would cost me dear." Keane Clason was waiting on the platform of a giant truck, the motor of which was idling. All the apparatus was in readiness except that the three demountable sections of the tower had yet to be run up into position. "One of the beauties of the D. P.," said Philip gleefully to the Doctor, while Keane smiled slyly to himself, "is that this pint-size dynamo provides all the current needed for the test. We pick the power for our radio right out of the air by means of a wave trap and mensurator invented by this bright little brother of mine," and he clapped Keane patronizingly on the back. "Yes, ah--Dr. Nukharin," ventured Keane timidly, and at that moment Quest experienced the raging red hatred that causes men to murder. "Philip has promised me that you will employ this device only as a threat to hold the ambitions of the larger powers in check." "Of course, of course!" replied the Doctor heartily. "But now let's have the test. Even at night I'm not too fond of these open-air performances." * * * * *