How could a man tell the difference if all the reality of Earth turned out to be a cosmic hoax? Suppose it turned out that this was just a stage set for students of history?

      *

      When the sharp snap of a pistol shot came from the half-finished building, Karnes wasn’t anywhere near the sandpile that received the slug. He was fifteen feet away, behind the much more reliable protection of a neat stack of cement bags that provided cover all the way to a window in the empty shell of brick and steel before him.

      Three hundred yards behind him, the still-burning inferno of what had been the Assembly Section of Carlson Spacecraft sent a reddish, unevenly pulsating light over the surrounding territory, punctuating the redness with intermittent flashes of blue-white from flaring magnesium.

      For an instant, Karnes let himself hope that the shot might be heard at the scene of the blaze, but only for an instant. The roar of fire, men, and machine would be too much for a little pop like that.

      He moved quietly along the stacked cement bags, and eased himself over the sill of the gaping window into the building. He was in a little hallway. Somewhere ahead and to his left would be a door that would lead into the main hallway where James Avery, alias James Harvey, alias half-a-dozen other names, was waiting to take another pot-shot at the sandpile.

      The passageway was longer than he had thought, and he realized that he might have been just a little careless in coming in through the window. With the firelight at his back, he might make a pretty good target from farther down the hall, or from any of the dark, empty rooms that would someday be officers’.

      Then he found it. The slight light from the main hallway came through enough to show him where to turn.

      Keeping in the darkness, Karnes’ eyes surveyed the broad hallway for several seconds before he spotted the movement near a stairway. After he knew where to look, it was easy to make out the man’s crouched figure.

      Karnes thought: I can’t call to him to surrender. I can’t let him get away. I can’t sneak across that hall to stick my gun in his ribs. And, above all, I cannot let him get away with that microfilm.

       Hell, there’s only one thing I can do.

      Karnes lifted his gun, aimed carefully at the figure, and fired.

      *

      Avery must have had a fairly tight grip on his own weapon, because when Karnes’ slug hit him, it went off once before his body spread itself untidily across the freshly set cement. Then the gun fell out of the dead hand and slid a few feet, spinning in silly little circles.

      Karnes approached the corpse cautiously, just in case it wasn’t a corpse, but it took only a moment to see that the caution had been unnecessary. He knelt, rolled the body over, unfastened the pants, pulled them down to the knees and stripped off the ribbon of adhesive tape that he knew would be on the inside of the thigh. Underneath it were four little squares of thin plastic.

      As he looked at the precious microfilm in his hand, he sensed something odd. If he had been equipped with the properly developed muscles to do so, he would have pricked his ears. There was a soft footstep behind him.

      He spun around on his heel, his gun ready. There was another man standing at the top of the shadowy stairway.

      Karnes stood up slowly, his weapon still levelled.

      “Come down from there slowly, with your hands in the air!”

      The man didn’t move immediately, and, although Karnes couldn’t see his face clearly in the shimmering shadows, he had the definite impression that there was a grin on it. When the man did move, it was to turn quickly and run down the upper hallway, with a shot ringing behind him.

      Karnes made the top of the stairway and sent another shot after the fleeing man, whose outline was easily visible against the pre-dawn light that was now beginning to come in through a window at the far end of the hall.

      The figure kept running, and Karnes went after him, firing twice more as he ran.

      Who taught you to shoot, dead-eye? he thought, as the man continued to run.

      At the end of the hall, the man turned abruptly into one of the offices-to-be, his pursuer only five yards behind him.

      *

      Afterwards, Karnes thought it over time after time, trying to find some flaw or illusion in what he saw. But, much as he hated to believe his own senses, he remained convinced.

      The broad window shed enough light to see everything in the room, but there wasn’t much in it except for the slightly iridescent gray object in the center.

      It was an oblate spheroid, about seven feet high and eight or nine feet through. As Karnes came through the door, he saw the man step through the seemingly solid material into the flattened globe.

      Then globe, man and all, vanished. The room was empty.

      Karnes