g. The massive beast rose on its hind
legs, growled, and Ross walked by it uncaring, unmenaced by the puzzled
animal.

Sometimes he slept through the dark periods which marked the nights, or
he stumbled along under the moon, nursing his hands against his breast,
whimpering a little when his foot slipped and the jar of that mishap ran
through his body. Once he heard singing, only to realize that it was
himself who sang hoarsely a melody which would be popular thousands of
years later in the world through which he wavered. But always Ross knew
that he must go on, using that thick stream of running water as a guide
to his final goal, the sea.

After a long while those spaces of mental clarity grew longer, appearing
closer together. He dug small shelled things from under stones along the
river and ate them avidly. Once he clubbed a rabbit and feasted. He
sucked birds' eggs from a nest hidden among some reeds--just enough to
keep his gaunt body going, though his gray eyes were now set in what was
almost a death's-head.

Ross did not know just when he realized that he was again being hunted.
It started with an uneasiness which differed from his previous
fever-bred hallucinations. This was an inner pulling, a growing
compulsion to turn and retrace his way back toward the mountains to meet
something, or someone, waiting for him on the backward path.

But Ross kept on, fearing sleep now and fighting it. For once he had
lain down to rest and had wakened on his feet, heading back as if that
compulsion had the power to take over his body when his waking will was
off guard.

So he rested, but he dared not sleep, the desire constantly tearing at
his will, striving to take over his weakened body and draw it back.
Perhaps against all reason he believed that it was the aliens who were
trying to control him. Ross did not even venture to guess why they were
so determined to get him. If there were tribesmen on his trail as well,
he did not know, but he was sure that this was now purely a war of
wills.

As the banks of the river were giving way to marshes, he had to wade
through mud and water, detouring the boggy sections. Great clouds of
birds whirled and shrieked their protests at his coming, and sleek water
animals paddled and poked curious heads out of the water as this
two-legged thing walked mechanically through their green land. Always
that pull was with him, until Ross was more aware of fighting it than of
traveling.

Why