Fortunately, sensor measurements had long since proved that the writhing was just another optical illusion. Those same measurements had also confirmed that the aptly named Coreline did indeed run along the exact geometric center of the Tube.

And that was all the sensors revealed. Most of the experts agreed that the Coreline was the key to how the Quadrail system operated—all except those who insisted it was the fourth rail, of course—but that was as far as anyone had ever gotten. No scanning equipment compact enough to fit through the Tube’s hatches had enough power to penetrate the Coreline’s outer skin to see what kind of equipment was tucked away inside, and the more powerful warship-class sensors couldn’t penetrate the outer wall of the Tube itself. Information stalemate, in other words, which was exactly how the Spiders liked it.

“Welcome, traveler,” a flat voice said in my ear.

Speak of the devils. Adjusting my expression to neutral, I turned around.

A Spider was standing behind me, a gray half-meter-diameter sphere hanging beneath an arching crown of seven segmented legs, the whole thing softly reflecting the Core-line’s ongoing light show. The whole thing was about twice my height, with the sphere hanging half a meter above my eye level, which marked this particular Spider as a maintenance drudge. That alone was noteworthy; usually it was the smaller conductors who did whatever communicating the Spiders deemed necessary. “Welcome yourself,” I replied wittily. “What can I do for you?”

“Where is your luggage?” it asked.

I looked back at the mass of bags being ferried up from the shuttle, some of them starting to roll away as their owners keyed their leashes. “Over there somewhere,” I said, pointing. “Why?”

“Please bring it here,” the Spider said. “It must be inspected.”

I felt my stomach tightening. In all my previous trips aboard the Quadrail the only times I’d seen anyone’s luggage pulled for inspection was when the Spiders’ unobtrusive sensor array had already decided there was something inside that violated their contraband rules. “Certainly,” I said, trying to sound calm as I tapped the leash button, hoping fervently that the bags wouldn’t embarrass me by dying halfway.