Harry pulled his chair a few inches forward, and the Guest, with an awkward sidling motion, came closer to the thick glass. Then it sat on the floor, leaving only its upper arms and long head visible. The three eyes pointed steadily at Harry, as if wishing to establish some unbreakable and facile rapport, or as if commiserating . . .

"Our world is doomed?" Harry asked, somehow avoiding all melodrama, giving the last word a perfectly straightforward and unstrained emphasis.

"Unless I sadly misknow your abilities, yes. This is bad news."

"It does seem so," Harry said. "What is the cause of this disease? Are you part of an army of conquest?"

"Conquest . . . Uncertain. Army?"

"Organized group of soldiers, fighters, destroyers and occupiers, invaders."

The Guest was silent and still for a few minutes. It might have been a statue but for the almost invisible throbbing of its upper crest. "I am a parasite, a happen-by voyager."

"Explain that, please."

"I am a flea, not a soldier or a builder. My world is dead and eaten. I travel here within a child of a machine that eats worlds."

"You've come on a spaceship?"

"Not my own. Not ours." The emphasis there was striking.

"Whose, then?" Harry pursued.

"Its forebears made by very distant people. It controls itself. It eats and reproduces."

Arthur trembled with confusion and fear and a deep anger he could not explain. "I don't understand," he said, blocking Harry's next words.

"It is a traveler that destroys and makes the stars safe for its builders. It gathers information, learns, and then eats worlds and makes new younger forms of itself. Is this clear?"

"Yes, but why are you here?" Arthur almost shouted.

"Shh," Harry said, holding up one hand. "It just said that. It's hitched a ride. It's a flea."

"You didn't build the rock, the spaceship or whatever it is, in the desert? That's not your vehicle?" Colonel Hall asked. Obviously, they had heard none of this before. Young Lieutenant Sanborn was visibly shaken.

"Not our vehicle," the Guest affirmed. "It is powerful enough not to fear our presence. We cannot hurt it. We sacrifice ..." Again it whistled. "We survive only to warn of the death our kind has met."

"Where are the pilots, the soldiers?" Harry asked.

"The machine does not live as we do," the Guest said.

"It's a robot, automatic?"

"It is a machine."

Harry pushed his chair back and rubbed his face vigorously with both hands. The Guest appeared to observe this closely, but otherwise did not change position.

"We have a couple of names for that kind of machine," Arthur said, facing Colonel Hall. "It sounds like a von Neumann device. Self-replicating, without outside instructions. Frank Drinkwater thinks the lack of such machines proves there is no intelligent life besides our own in the galaxy."

"Playing devil's advocate, no doubt," Harry said, still massaging the bridge of his nose. "What scientist would want to prove intelligence was unique?"