Snap and I decided to walk part of the way back to the ship. It was barely more than a mile through this subterranean corridor to where we could get the vertical lift direct to the landing stage.
We started off on the lower level. Once outside the insulation of Halsey's office we did not dare talk of this thing. Not only electrical ears, but every possible eavesdropping device might be upon us. The corridor was two hundred feet or more below the ground level. At this hour of the night the business section was comparatively deserted. The stores and office arcades were all closed.
Our footfall echoed on the metal grids as we hurried along. I felt depressed and oppressed. As though prying eyes were upon me. We walked for a time in silence, each of us busy with memory of what had transpired at Halsey's office.
Suddenly Snap gripped me. "What's that?"
"Where?" I whispered.
We stopped at a corner. An entryway was here. Snap pulled me into it. I could feel him quivering with excitement.
"What is it?" I demanded in a whisper.
"We're being followed. Did you hear anything?"
"No!" Yet I thought now that I could hear something. Vague footfalls. A rustling. And a microscopic whine, as though some device were within range of us.
Snap was fumbling in his pocket. "Wait! I've got a pair of low-scale detectors."