"Never talk secretly to me," he murmured. "No insulation here. You take care of Miss Blake. Say nothing--keep your eyes wide. When we get to the Moon--" I stiffened, went cold, with my heart suddenly pounding. My hand darted out, gripped the captain's arm. "Wait!" I murmured. On my chest, underneath my shirt, a flat, round little detector-grid was abruptly glowing warm against my flesh. An interference current was overcharging its low-pressure wires so that they were heating and burning me. An eavesdropping current! No one save a Government criminal-tracker may legally use an eavesdropping ray. But there was one here, listening to us now! I murmured it to Mackensie; turned and darted away. A dim door oval was nearby. I went through it, into a narrow, tube-lit corridor of the ship's superstructure. Momentarily no one was here; there was just the dim, vaulted little arcade, gleaming pallidly silver from its fittings and trim of alumite with rows of cabin doorways on each side. The name-plates glowed with the names of the occupants for this voyage. All the doors were closed; a few faint voices from passengers in the cabins were vaguely audible. * * * * * At a cross-corridor I stopped. Was someone here able to watch me? From my shirt I drew out the little detector-grid. It was cooling now, but still its direction needle was swaying. The source of the current seemed ahead of me in this cross corridor. How far, I could not say--the distance gauge-point was swiftly dropping to zero. The eavesdropping current had been snapped off. Wherever he was, this listener knew now that we were aware of him. On my padded, felt-soled shoes I dashed ahead to where the corridor widened into a tiny smoking lounge. "Oh, you Penelle? What's the matter? Can't you find your cubby?" It was Dr. Frye, the ship's surgeon. Fortunately, he did not see the Banning heat-flash gun in my hand. He was sprawled here in a chair, smoking. His thin face grinned up at me. "Ask the purser your location," he added. His gesture waved me toward the purser's tiny office-cubby down the opposite corridor. "Thanks," I agreed. The purser's cubby was unoccupied. I passed it, came to the stern end where the superstructure stopped and the side decks converged into a triangle of open deck under the dome at the pointed stern. There were a few passengers lounging around and deckhands moving at their tasks of uncradling the vessel which now was ready to take off. Over at a glassite bull's-eye window in the side pressure-wall, the big Martian, Set Mokk, was standing, gazing at the people on the lower stage.