into two complete sets! There were two television cameras, identical in every way, one in Dave's world, one in the everyday world, placed in perfect register!

His proof!

His friends had gone; obviously back to their laboratory to prepare another crystal. Here he could get one: their next one. Then he could communicate with them and start planning a counter-offensive.

Dave looked across the plain towards the main laboratory building, and shrugged. If he had a crystal now, all he could do would be to let them know he was alive and on the job, but had no information. On the other hand, he had fouled up the television camera in the remote lab, and it seemed likely that there would be a repairman coming along to see what was wrong.

Just where Claverly and Phelps were in this mess Dave didn't know. But he assumed that soon after their projection into this cockeyed half-world, the enemy had come along to collect them both.

Dave blinked at a sudden fantastic thought: would the flashing of a crystal send him back to his own world, or toss him along into another one?

An interesting thought—to be pursued later. Right this moment the thing to do was to lie doggo until the enemy arrived to take Dave in tow. This time, instead of a baffled scientist, they were attempting to catch a gent who was more interested in being alive than in figuring out where he was.

Had Dave been a pure scientist, he would have been amazed and baffled by this half-world. The whys and wherefores would have bothered him to the exclusion of other considerations, and he would have been standing there trying to figure it all out when the enemy came along to collect him. Instead, Dave was still alive, or felt that he was, and that was enough for him. Someone else could figure out how and why; his was the line of action; so long as he was able, he was going to continue to live and fight.

So when the helicopter dropped down out of the sky near the remote laboratory and disgorged a man carrying a rifle, Dave, the quarry, was sprawled behind a slight ridge in the half-world's terrain, watching through a cleft in the stone outcrop.

CHAPTER FOUR

The Struggle for Earth

The man with the rifle prowled around the ship, looking carefully out across the plains.

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