As soon as Gibbons had our word, he extinguished the knob light, and the knob, as well as the wire, became totally invisible. At our ultrophoned word, he would light it again.
"No gun play now," I warned. "Swords only, and then only if absolutely necessary."
Closely bunched, and treading as lightly as only inertron-belted people could, we made our way cautiously through a door and down an inclined plane to the floor below, where Gaunt and Blash assured us the military offices were located.
Twice Barker cautioned us to stop as we were about to pass in front of mirror-like "windows" in the passage wall, and flattening ourselves to the floor, we crawled past them.
"Projectoscopes," he said. "Probably on automatic record only, at this time of night. Still, we don't want to leave any records for them to study after we're gone."
"Were you ever here before?" I asked.
"No," he replied, "but I haven't been studying their electrophone communications for seven years without being able to recognize these machines when I run across them."