"but I cannot see that
it has any relevancy today. The past is unchangeable and we must fight
in the present. That is enough to occupy all our energies."

Jason felt too exhausted to argue the point any more. He ran into the
same stone wall with all the Pyrrans. Theirs was a logic of the moment.
The past and the future unchangeable, unknowable--and uninteresting.
"How is the perimeter battle going?" he asked, wanting to change the
subject.

"Finished. Or in the last stages at least," Brucco was almost
enthusiastic as he showed Jason some stereos of the attackers. He did
not notice Jason's repressed shudder.

"This was one of the most serious breakthroughs in years, but we caught
it in time. I hate to think what would have happened if they hadn't been
detected for a few weeks more."

"What are those things?" Jason asked. "Giant snakes of some kind?"

"Don't be absurd," Brucco snorted. He tapped the stereo with his
thumbnail. "Roots. That's all. Greatly modified, but still roots. They
came in under the perimeter barrier, much deeper than anything we've had
before. Not a real threat in themselves as they have very little
mobility. Die soon after being cut. The danger came from their being
used as access tunnels. They're bored through and through with animal
runs, and two or three species of beasts live in a sort of symbiosis
inside.

"Now we know what they are we can watch for them. The danger was they
could have completely undermined the perimeter and come in from all
sides at once. Not much we could have done then."

[Illustration]

The edge of destruction. Living on the lip of a volcano. The Pyrrans
took satisfaction from any day that passed without total annihilation.
There seemed no way to change their attitude. Jason let the conversation
die there. He picked up the log of the _Pollux Victory_ from Brucco's
quarters and carried it back to his room. The wounded Pyrrans there
ignored him as he dropped onto the bed and opened the book to the first
page.

For two days he did not leave his quarters. The wounded men were soon
gone and he had the room to himself. Page by page he went through the
log, until he knew every detail of the settlement of Pyrrus. His notes
and cross-references piled up. He made an accurate map of the original
settlement, superimposed over a modern one. They didn't match at all.

It was a dead end. With one map held over the other, what he had
suspected was painfully clear. The descripti