Everyone loves a free spender, and I was all of that. The one-eyed landlord muttered and snaffled to himself and managed to find a drinkable bottle of claret in his cellar which I kept for myself. The locals were more than happy to consume blackjack after blackjack of ale. These containers were made of leather covered with tar which added a certain novelty to the flavor, but the customers did not seem to mind. My best informant was a bristle-bearded drover named Quinch. He was one of the men who moved the cattle from the pens to the knackers' yard where he also assisted the butchers in their bloody tasks. His sensibilities, as one might suspect, were not of the highest, but his capacity for drink was, and when he drank, he talked, and I hung on every word. He entered and left London every day, and bit by bit, through the spate of profanity and abuse, I put together what I hoped was an accurate picture of the entrance procedures.
There was a search; that much I could see from my window. At times a close search, at other times superficial. But there was one part of the routine that never varied.
Every person entering the city had to put his hand into a hole in the wall of the guardhouse. That was all, just put it in. Not touch anything at all, just in up to the elbow and out.
Over this I brooded, sipping my wine and ignoring the roars of masculine cheer around me. What could they detect from this? Fingerprints perhaps, but I always wore false fingerprint covers as a matter of routine and had changed these three times since the last operation. Temperature? Skin alkalinity? Pulse or blood pressure? Could these residents of, what to me was, the dim past differ in some bodily composition? It was not unreasonable to expect some changes over a period of more than 30,000 years. I had to find out the present norms.
This was done easily enough. I constructed a detector that could record all these factors and hung it inside my clothing. The pickup was disguised as a ring that I wore on my right hand. The next evening I shook hands with everyone I could, finished my wine, and retired to my chamber. The recordings were precise, accurate to 0. 006 percent and very revealing. Of the fact that my personal readings fell well inside all the normal variations.
"You are not thinking, Jim," I accused myself in the warped mirror. "There has to be a reason for that hole in the wall. And the reason is a detection instrument of some kind. Now what does it detect?" I turned away from the accusing stare. "Come, come, don't evade the question. If you cannot answer it that way, turn it on its head. What is it possible to detect?"
This was more like it. I pulled out a piece of paper and began to list all the things that can be observed and measured, going right down the frequencies. Light, heat, radio waves, etc., then off into vibration and noise, radar reflections, anything and everything, not attempting to apply the things detected to the human body. Not yet. I did this after I had made the list as complete as possible. When I had covered the paper, I shook hands with my self triumphantly and reread it for human applications.
Nothing. I was depressed again. I threw it away—then grabbed it back. Something, what was it, something relating to something I had heard about Earth. What? Where. There! Destroyed by atomic bombs Coypu had said.
Radioactivity. The atomic age was still in the future, the only radioactivity in this world was natural background radiation. This did not take long to check.
Me, creature of the future, denison of a galaxy full of harnessed radiation. My body was twice as radioactive as the background count in the room, twice as radioactive as the hot bodies of my friends in the bar when I slipped down to check them out.
Now that I knew what to guard against I could find a way to circumvent it. The old brain turned over, and soon I had a plan, and well before dawn I was ready to attack. All the devices secreted about my person were of plastic, undetectable by a metal detector if they had one working. The items that were made of metal were all in a plastic tube less than a meter long and no thicker than my finger, which I coiled up in one pocket. In the darkest hour before the dawn I slipped out and stalked the damp streets looking for my prey.
And found him soon enough, a French sentry guarding one of the entrances to the nearby docks. A quick scuffle, a bit of gas, a limp figure, a dark passageway. Within two minutes I emerged at the opposite end wearing his uniform with his gun on my shoulder carried in the correct French manner. With my tube of devices down its barrel. Let them find that metal with a detector. My timing was precise, and when, at the first light, the straggling members of the night guard returned to London, I was marching in the last row. I would enter, undetected, in the ranks of the enemy. A foolproof scheme. They wouldn't examine their own soldiers.