The arrest of Johnson had caused considerable comment among the passengers. A few had seen me drag him forward to the cage. The incident had been the subject of passenger discussion all afternoon. Captain Carter had posted a notice to the effect that Johnson's accounts had been found in serious error, and that Dr. Frank for this voyage would act in his stead. * * * * * It was near midnight when Snap and I closed and sealed the helio-room and started for the chart-room, where we were to meet with Captain Carter and the other officers. The passengers had nearly all retired. A game was in progress in the smoking room, but the deck was almost deserted. Snap and I were passing along one of the interior corridors. The stateroom doors, with the illumined names of the passengers, were all closed. The metal grid of the floor echoed our footsteps. Snap was in advance of me. His body suddenly rose in the air. He went like a balloon to the ceiling, struck it gently, and all in a heap came floating down and landed on the floor! "What in the infernal!--" He was laughing as he picked himself up. But it was a brief laugh. We knew what had happened: the artificial gravity-controls in the base of the ship, which by magnetic force gave us normality aboard, were being tampered with! For just this instant, this particular small section of this corridor had been cut off. The slight bulk of the Planetara, floating in space, had no appreciable gravity pull on Snap's body, and the impulse of his step as he came to the unmagnetized area of the corridor had thrown him to the ceiling. The area was normal now. Snap and I tested it gingerly. He gripped me. "That never went wrong by accident, Gregg! Someone down there--" * * * * * We rushed to the nearest descending ladder. In the deserted lower room the bank of dials stood neglected. A score of dials and switches were here, governing the magnetism of different areas of the ship. There should have been a night operator, but he was gone. Then we saw him lying nearby, sprawled face down on the floor! In the silence and dim lurid glow of the fluorescent tubes, we stood holding our breaths, peering and listening. No one here. The guard was not dead. He lay unconscious from a blow on the head. A brawny fellow. We had him revived in a few moments. A broadcast flash of the call-buzz brought Dr. Frank in haste from the chart-room. "What's the matter?" We pointed at the unconscious man. "Someone was here," I said hastily. "Experimenting with the magnetic switches. Evidently unfamiliar with them--pulling one or another to test their workings and so see the reactions on the dials." We told him what had happened to Snap in the upper corridor. Dr. Frank revived the guard in a moment. He was no worse off for the episode, save a lump on his head, and a nasty headache.