“A Scottish astronomer,” Arthur explained. “He made a fair mess of a controversy about twenty-three years ago when he claimed to have evidence of an alien space probe orbiting near the Earth. A probe he thought might be from Epsilon Bootis. His evidence consisted of patterns of anomalous returned radio signals that seemed to have been bounced from an object in space. Like a great many pioneers, he had to face disappointment and recant, after a fashion.”

“No, sir,” Hall said, again with his enigmatic smile. “We haven’t spoken to Mr. Lunan.”

“Pity. I can think of a hundred scientists who should be here,” Arthur said.

“Eventually, perhaps,” Hall allowed. “Not right now.”

“No. Of course not. Well?” Arthur gestured at the dark window.

“Colonel Phan will give us a direct view in a few minutes.”

“Who is Colonel Phan?” Harry asked.

“He’s an expert in space medicine from Colorado Springs,” Hall said. “We couldn’t find anyone better qualified on such short notice, although I doubt we could find a better man for the job even if we searched all year.”

“You didn’t ask us,” Harry said. Arthur nudged him gently in the arm.

The lights in the viewing room dimmed. “I hope someone’s making videotapes of our Guest,” Harry whispered pointedly to Arthur as they pulled their seats close to the window.

“We have a digital recorder and three high-resolution cameras working around the clock,” Lieutenant Sanborn explained.

“All right,” Harry said.

Harry was obviously nervous. For his own part, Arthur felt both alert and vaguely anesthetized. He could not quite accept that an age-old question had been answered affirmatively, and that they were about to see the answer.

The black curtain drew aside. Beyond another thick pane of glass framed in stainless steel, they saw a small, dimly lighted, almost empty square room, watery green in color. In the middle of the room was a low platform draped with what appeared to be blankets. A plastic beaker of clear water sat in one corner. In the right-hand corner nearest their window was a meter-tall transparent cylinder, open at the top. Arthur took all this in before focusing on what lay under the blankets on the low table.

The Guest moved, raised a forward limb — clearly a kind of arm, with a three-fingered hand, each finger divided in two above the middle joint — and then sat up slowly, the blanket falling free of its wedge-shaped head. The long “nose” of its head pointed at them and the golden brown eyes emerged from the blunt end, withdrew, emerged. Arthur, mouth dry, tried to see the being as a whole, but for the moment could only concentrate on whether the eyes were lidded, or actually withdrew within “pools” of pale gray-green flesh.

“Can we speak to it?” Harry asked Hall over his shoulder.

“There’s two-way communication with the room.”

Harry sat in a seat near the window. “Hello. Can you hear us?”

“Yes,” the Guest said. Its voice was sibilant and weak but clearly understandable. It lowered itself to the floor and stood uncertainly beside the low table. Its lower limbs — legs — were jointed in reverse, yet not like a dog’s or horse’s hind legs, where the “knee” is the analog of a human wrist. The Guest’s articulation was quite original, each joint actually reversed, with the limb’s lower half dropping smoothly, gracefully, to split into three thick extensions, the tip of each extension splayed into two broad “toes.” The legs made up much of its height, its rhinoceros-hide “trunk” occupying only about half a meter of its full meter and a half. The end of the long head, thrust forward on a thick, short neck, dropped a few centimeters below the juncture of legs and trunk. The arms rose from each side of the trunk like the folded manipulators of a mantis.

Harry scowled and shook his head, temporarily unable to speak. He waved a hand in front of his mouth, glancing at Arthur, and coughed.

“We don’t know quite what to say to you,” Arthur finally managed. “We’ve been waiting a long time for someone to visit the Earth from space.”

“Yes.” The Guest’s head swung back and forth, the jewel-bright, moist, sherry-colored eyes fully revealed. “I wish I could bring better words on such an important occasion.”

“What…ah, what words do you bring?” Harry asked.

“Are you related?” the Guest asked in turn.

“I’m sorry — related?”

“There is a question about my communication?”

“We are not of the same family — not siblings, brother or father and son or…whatever,” Arthur said.

“You have a social relationship.”

“He’s my boss,” Harry said, pointing to Arthur. “My hierarchical superior. We’re friends, also.”

“And you are not the same individuals in different form as the individuals behind you?”

“No,” Harry said.

“Your forms are steady.”

“Yes.”

“Then…” The Guest made a sharp, high-pitched whistling noise, and the long crest above the level of the shoulders appeared to inflate slightly. Arthur could not see a mouth or nose near the eyes, and surmised such openings might be on the head below the neck and facing the chest, in the area corresponding — if such correspondences were at all useful — to a long “chin.” “I will relate my bad news to you, as well. Are you placed highly in your group, your society?”

“Not the highest, but yes, we are highly placed,” Harry said.

“The news I bring is not happy. It may be unhappy for all of you. This I have not spoken before in detail.” Again the whistling noise. The head lifted and Arthur spotted slitlike openings on the underside. “If you have the ability to leave, you will wish to do so soon. A disease has entered your system of planets. There is little time left for your world.”

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.”