To kill from ambush meant that they might never learn the secret of the machine, but after his experience Travis was willing to admit that Nolan's caution was the wise way. Travis wanted no part of a second attack like that which had shaken him so. And Nolan had not ordered a general retreat. It must be in the war chief's thoughts as it was in Travis' that if the machine could have an influence over Apaches, it must cease to function.

They set their ambush with the age-old skill the Redax had grafted into their memories. Then there was nothing to do but wait.

It was an hour after dawn when Tsoay signaled that the enemy was coming, and shortly after, they heard the thud of ponies' hoofs. The first Tatar plodded into view, and by the stance of his body in the saddle, Travis knew the Red had him under full control. Two, then three Tatars passed between the teeth of the Apache trap. The fourth one had allowed a wider gap to open between himself and his fellows.

Then the Red leader came. His face below the bulge of the helmet was not happy. Travis believed the man was not a horseman by inclination. The Apache set arrow to bow cord, and at the chirp from Nolan, fired in concert with his clansmen.

Only one of those arrows found a target. The Red's pony gave a shrill scream of pain and terror, reared, pawing at the air, toppled back, pinning its shouting rider under it.

The Red had had a defense right enough, one which had somehow deflected the arrows. But he neither had protection against his own awkward seat in the saddle nor the arrow which had seriously wounded the now threshing pony.

Ahead the Tatars twisted and writhed, mouthed tortured cries, then dropped out of their saddles to lie limply on the ground as if the arrows aimed at the master had instead struck each to the heart.

11

Either the Red was lucky, or his reactions were quick. He had somehow rolled clear of the struggling horse as Lupe leaped from behind a boulder, knife out and ready. To the eyes of the Apaches the helmeted man lay easy prey to Lupe's attack. Nor did he raise an arm to defend himself, though one hand lay free across the plate on his chest.

But the young Apache stumbled, rebounding back as if he had run into an unseen wall....when his knife was still six inches away from the other. Lupe cried out, shook under a second impact as the Red fired an automatic with his other hand.

Travis dropped his bow, returned to the most primitive weapon of all. His hand closed around a stone and he hurled the fist-sized oval straight at the helmet so clearly outlined against the rocks below.

But even as Lupe's knife had never touched flesh, so was the rock deflected; the Red was covered by some protective field. This was certainly nothing the Apaches had seen before. Nolan's whistle summoned them to draw back.