“It’s one of those big e-ring devices we saw on the way in,” said Daeman.

“A linear accelerator with its wormhole collection ring,” said Prospero. “The post-humans were so proud of these things. As you saw, they made thousands.”

“So?” said Harman. “Are you saying that the fax system on Earth is controlled by these things?”

Prospero shook his brow-heavy head. “Your fax system is terrestrial. It doesn’t move bodies through space and time, only data. But these wormhole collectors are the spiders in the center of the post-humans quantum teleportation web.”

“So?” said Harman again. “We just want to go back to Earth.”

“Grip that green controller and squeeze the red circle twice,” said Prospero.

Daeman did so. On the holographic display of the orbital linear accelerator, a small quad of engine thrusters pulsed twice, sending a tiny silver cone of crystallized exhaust into space. The long array of girders, tanks, columns, and rings began to rotate ever so slowly. Counter-thrusters fired just as briefly, and the long accelerator stabilized. The fifty-meter-wide shimmering wormhole at its end, centered within the huge and gleaming collection ring, had not turned with the accelerator. Daeman leaned close to the holographic image of the accelerator and saw that the collection ring was on gimbals. He reached a finger into the image, touched different elements, and saw the vid image shift into diagrams and descriptive lettering—return line, injector, quad thrusters. He removed his hand and the real-time image reappeared. The words had, of course, meant nothing to him.

“Attitude control, orbital translation thrusters,” said Prospero. “This asteroid is in stable orbit—it would be a possible species-extinction event if it fell onto the Earth—but the wormhole collecting accelerators and the Casimir mirrors were constantly being moved around.”

“From here,” said Daeman.

Prospero nodded. “And from the other asteroid cities.”

Harman and Daeman looked at each other again. “There are more post-human cities?” asked Harman.

“Three more,” said the magus. “One other on this equatorial ring. Two on the polar ring.”

“Are there living post-humans there?” asked Daeman. He suddenly saw an alternative to all this destruction and the end of the Five Twenties way of life.

“No.” Prospero sat in his high-backed chair. “And there are no other firmaries, either. This city was the only one that bothered itself with the affairs of you modified old-styles down there.” He waved a mottled hand toward the Earth rising on the right curve of the dome. The room was suddenly brightened again by Earthlight.

“All the posts are dead,” repeated Daeman.

“No, not dead,” said Prospero. “Gone elsewhere.”

Daeman looked at the limb of the Earth rising and the blackness of space above the shimmering curve of atmosphere. “Gone where?”

“Mars, to begin with,” said the magus. He looked at their quizzical expressions and chuckled. “Do either of you modern men have any idea where Mars is? What Mars is?”

“No,” said Daeman without embarrassment. “Will the posts be coming back from there?”

“I think not,” said Prospero, still smiling.

“Then it doesn’t matter, does it?” said Harman. “Prospero, were you suggesting we could use this . . . particle accelerator wormhole thing . . . as a weapon?”

“As the ultimate weapon against this city,” said Prospero. “Common explosives or weapons would have little effect on the crystal city or its asteroid. These towers are made to withstand actual meteor impact. But three kilometers and more of heavy-mass exotic materials with a wormhole on its snout, under thrust, will have a definite impact, especially if you target it directly on the firmary.”

“Will Caliban survive?” asked Daeman.

Prospero shrugged. “His tunnels and grottoes have saved him before. But perhaps such a collision will provide a Caliban-species extinction event here of its own.”

“Can he escape before it hits?” asked Harman.

“Only if he learns of the sonie and takes possession of one of your thermskin suits,” said Prospero. Then he smiled disconcertingly, as if such a prospect was not totally improbable.

“How long will it take for this accelerator-monstrosity to get here?” asked Daeman. “Until impact?”

“You can program it to arrive as quickly or slowly as you wish,” said the magus, rising and walking into the center console, his lower body disappearing into the metal and virtual panels. He raised one arm, the robe slid back a bit, and the skinny forearm and bony finger pointed to the end of the accelerator away from the wormhole ring. “Right here,” said Prospero, “are the plane-change thrusters—the most powerful engines. I’ll show you how to activate them and to aim this weapon.”

The two followed his instructions on rotating the accelerator and programming what Prospero called its trajectory coordinates and delta-v. Daeman’s finger hovered above the initiate virtual button. “You didn’t tell us how long we have until impact,” he said to Prospero.

The hologram steepled its fingers. “Fifty hours sounds right. An hour for you to get to the firmary and take control. Forty-eight hours to allow the new arrivals to heal and to fax them all back intact. An hour then to find your way to the sonie and escape before this little world ends.”

“No time to sleep?” said Harman.

“I would advise against it,” said Prospero. “Caliban will probably be trying to kill you every minute of that time.”

Harman and Daeman exchanged glances. “We can take turns napping and eating and keeping watch at the controls there,” said Daeman. He hefted the pistol and then set it back in Savi’s pack. “We’ll keep Caliban at bay.”

Harman nodded doubtfully. He looked very, very weary.

Daeman looked at the real-time image of the linear accelerator again and set his thumb above the thruster initiate button again. “Prospero, you’re sure this won’t end all life on Earth or anything?”

The magus chuckled. “All life as you know it, yes,” he said. “But no flaming asteroid from the sky species-extinction event. At least I don’t believe so. We’ll have to see.”

Daeman looked at Harman, whose own hands were wrist-deep in the virtual panel. “Do it,” said Harman.

Daeman pushed the button. On the display above the holographic projector, eight huge thrusters at the end of the linear accelerator lit up with solid, continuous pulses of blue-ion ignition. The long structure shuddered slightly and began to move slowly—directly toward Daeman’s and Harman’s faces.

“Good-bye, Prospero,” said Daeman, grabbing Savi’s pack and turning toward the semipermeable exit.

“Oh, no,” said Prospero. “If you make it to the firmary, I’ll be there. I wouldn’t miss the next fifty hours for the world.”

I leave the burning city in search of Achilles and see chaos stretching all the way to the sea. Trojans and Achaeans alike are pulling bodies from smoking craters from the Scaean Gates to the surf’s edge, and everywhere confused men are helping their wounded comrades back to Ilium or across the defensive trench into the Greek camps. As with most aerial bombardments in my era, the effects of the attack were more terrifying than the results. I imagine that there are several hundred dead—Trojan and Achaean warriors and civilians in Ilium all included—but most escaped unharmed, especially out here away from falling walls and flying masonry.

As I’m clambering over the lowest part of Thicket Ridge, I see the little robot coming toward me, tugging along his floating crabshell friend like a little boy pulling an especially large Radio Flyer wagon. For some reason, I’m so pleased to see them alive—although “still in existence” might be a better term—that I come very close to crying.