secrets--walling
off the world the beetles knew from the unknown beyond. Involuntarily
Dworn shivered. He couldn't be sure--but it seemed to him that the
destroyers had come from over the Barrier and had flown back there.

He set his machine in cautious motion again and stole along, making
northward and keeping close to the Barrier. It occurred to him that the
beetle horde, routed and fleeing, might well have hugged the cliffs for
protection against flying foes.

The going here was not easy. The terrain seemed increasingly unfamiliar
though he should have known every foot of it. But--he remembered no
such tumbled crags, no such great heaps of stony detritus as blocked his
way and forced him into long detours....

Finally he halted to take his bearings, and, looking up, discovered what
had happened. The black rampart of the Barrier was notched and broken.
Sometime in the past year, since Dworn had left this place to begin his
wandering, a quarter-mile-wide section of the upper crags, hollowed and
loosened by the slow working of millennial erosion, had fallen and
spilled millions of tons of rock crashing and shattering onto the slopes
below. Here now water would run when the rains fell, and in ten or
twenty thousand years, perhaps, a river-course would have completed the
breach.

Dworn wondered fleetingly whether any living thing had been here when
the cliffs fell. If so, it was buried now, crumbling bone and corroding
metal, under the mountain for all time to come.

He set about skirting the rockfall, still searching the ground for
traces of beetle wheels. But there were very few wheel or tread marks of
any description to be seen--and that was strange in itself.

Impulsively he halted again and listened, his amplifier turned up. He
should have heard faroff engine-mutterings, occasional explosions from
the desert to the west, where normally the predatory machines and their
victims prowled and fought all night long over the sandy tracts and the
desolate ridges.... But there was nothing. A silence, vast and
unnatural, lay upon the wastes in the shadow of the high plateau.

He looked up again at the fallen rampart of the Barrier. The great
landship had opened, as it were, a gateway to the unknown lands in the
east--a gateway for what?

There was a strangeness here since last year, and the strangeness crept
chillingly into Dworn's blood, made the mountain air seem thin and cold.

As he started again, he noticed yet