The guard leaned back. The city of Buenos Aires spread out below them. The tumbled, congested old business quarter glittered in all its offices, and the broad Avenida de Mayo cut its way as a straight slash of glittering light through the section of the city to eastward. By contrast, from above, the far-flung suburbs seemed dark and somber. The big plane roared above the city, settling slowly; banked steeply and circled upon its farther side, and dipped down toward what seemed an absurdly small area, which sprang into a pinkish glow on their descent. That area spread out as the descent continued, though, and was a wide and level field when the ship flattened out and checked and lumbered to a stop. A glistening black car came swiftly, humming into place alongside almost before the clumsy aircraft ceased to roll. Its door opened. Two men got out and waited. The hangars were quite two hundred yards away, and Bell saw the glitter of weapons held inconspicuously but quite ready. He stepped out of the cabin of the plane with a revolver muzzle pressing into his spine. Other revolver muzzles pressed sharply into his sides as he reached earth. Smiling faintly, he took four steps, clambered up into the glistening black car, and settled down comfortably into the seat. The two men who had waited by the car followed him. The door closed, and Bell was in a padded silence that was acutely uncomfortable for a moment. A dome light glowed brightly, however, and he lighted nearly the last of the cigarettes from Asuncion with every appearance of composure as the car started off with a lurch. * * * * * The windows were blank. Thick, upholstered padding covered the spaces where openings should have been, and there was only the muffled vibration of the motor and the occasional curiously distinct noise of a flexing spring. "Just as a matter of curiosity," said Bell mildly, "what is the excuse given on the flying field for this performance? Or is the entire staff subject to The Master?" Two revolvers were bearing steadily upon him and the two men watched him with the unwavering attention of men whose lives depend upon their vigilance. "You, Senor," said one of them without expression or a smile, "are the corpse of a prominent politician who died yesterday at his country home." And then for half an hour or more the car drove swiftly, and stopped, and drove swiftly forward again as if in traffic. Then there were many turns, and then a slow and cautious traverse of a relatively few feet. It stopped, and then the engine vibration ceased. "I advise you, Senor," said the same man who had spoken before, and in the same emotionless voice, "not to have hope of escape in the moment of alighting. We are in an enclosed court and there are two gates locked behind us." Bell shrugged as there was the clatter of a lock operating. The door swung wide. * * * * *