Light flared, dazzling her. She flinched, raising her hand. When she could see again, she made out a pall of black smoke, rising from somewhere to the south of the river, its origin lost in murky smog. Then a shock wave reached the Society building. The tough old structure shuddered, and the window creaked. She heard a more remote tinkle of glass, the blaring of alarms, and screams.

It had been an explosion, a big one. The cosmologists murmured, grave and apprehensive.

Toby Pitt touched her shoulder. His face had lost all its humor now. “Siobhan. We’ve had a call from the Mayor’s office. They’re asking for you.”

“Me? …” She glanced around, feeling lost. She had no idea what was happening. “The conference—”

“I think everybody will accept a postponement, in the circumstances.”

“How can I get there? If that mess outside is typical—”

He shook his head. “We can videoconference from here. Follow me.”

As she followed his broad-shouldered form out of the City Rooms, she raised her own phone. “Mother?”

“You’re still there? All I heard was chattering.”

“That’s cosmologists for you. I’m fine, Mother. And you—”

“So am I. That bang was nowhere near me.”

“Good,” Siobhan said fervently.

“I phoned Perdita. The line was bad, but she’s all right. They’re keeping them at college until things settle down.”

Siobhan felt huge, unreasonable relief. “Thank you.”

Maria said, “The doctors are running everywhere. Their pagers seem to be on the blink. You’d think casualties would be coming in but I’ve seen nobody yet … Do you think it was terrorists?”

“I don’t know.” Toby Pitt had reached the door and was beckoning her. “I’ll try to keep the connection open.” She hurried from the room.

The rover reached the Station long before Mikhail had clambered his way back down the trail. The visitor waited at the hab entrance with an impatience the surface suit couldn’t disguise.

Mikhail thought he recognized the figure just by his stance. Though its population was scattered around its globe, on the human scale the Moon was a very small town, where everybody knew everybody else.

Thales confirmed it in a whisper. “That is Doctor Eugene Mangles, the notorious neutrino hunter. How exciting.”

That cursed computer-brain is teasing me, Mikhail thought irritably; Thales knows my feelings too well. But it was true that his heart beat a little faster with anticipation.

Encased in their suits, Mikhail and Eugene faced each other awkwardly. Eugene’s face, a sculpture of planed shadows, was barely visible through his visor. He looked very young, Mikhail thought. Despite his senior position Eugene was just twenty-six—a maverick boy genius.

For a moment Mikhail was stuck for something to say. “I’m sorry,” he said. “I don’t get too many visitors out here.”

Eugene’s social skills seemed even more underdeveloped. “Have you seen it yet?”

Mikhail knew what he meant. “The sun?”

“The active region.”

Of course this boy had come here for the sun. Why else visit a solar weather station? Certainly not for the crusty, early-middle-aged astrophysicist who tended it. And yet Mikhail felt a foolish, quite unreasonable pang of disappointment. He tried to sound welcoming. “But don’t you work with neutrinos? I thought your area of study was the core of the sun, not its atmosphere.”

“Long story.” Eugene glared at him. “This is important. More important than you know, yet. I predicted it.”

“What?”

“The active region.”

“From your studies of the core? I don’t understand.”

“Of course you don’t,” Eugene said, apparently careless of any offense he might cause. “I logged my predictions with Thales and Aristotle, date-stamped to prove it. I’ve come here to confirm the data. It’s come to pass, just as I said it would.”

Mikhail forced a smile. “We’ll talk it over. Come inside. You can see as much data as you want. Do you like coffee?”

“They have to listen,” said Eugene.

They? … “About what?”

“The end of the world,” Eugene said. “Possibly.” He led the way into the dustlock, leaving Mikhail standing openmouthed.

They didn’t talk as they worked their way through dustlock and airlock into the hab. Every human on the Moon was still a pioneer, and if you were smart, no matter what was on your mind, as you moved from one safe environment to another through seals and locks and interfaces and in and out of EVA suits, you concentrated on nothing but the life-preserving procedures you were going through. If you weren’t smart, of course, you would be lucky if you were forcibly shipped out before you killed yourself, or others.

Mikhail, slick with daily practice, was first out of his EVA suit. As the suit slithered to its cleaning station—somewhat grotesquely, its servos dragging it across the floor like an animated flayed skin—Mikhail, in his underwear, went to a sink where he scrubbed his hands in a slow trickle of water. The gray-black dust he had picked up handling the suit, grimy despite the dustlock’s best efforts, had rubbed into his pores and under his nails, and was burning slowly with his skin’s natural oils, giving off a smell like gunpowder. The Moon’s dust had been a problem since the first footsteps taken here: very fine, getting everywhere, and oxidizing enthusiastically whenever it got the chance, the dust corroded everything from mechanical bearings to human mucous membranes.

Of course it wasn’t the engineering problems of Moon dust that were on Mikhail’s mind right now. He risked a look around. Eugene had taken off boots and gloves, and he lifted his helmet away, shaking his beautiful head to free up thick hair. That was the face Mikhail remembered, the face he had first glimpsed at some meaningless social function in Clavius or Armstrong—a face freshly hardened into manhood, but with the symmetry and delicacy of boyhood, even if the eyes were a little wild—the face that had drawn him as helplessly as a moth to a candle.

As Eugene stripped off his spacesuit Mikhail couldn’t help dwelling on an old memory. “Eugene, have you ever heard of Barbarella?”

Eugene frowned. “Is she at Clavius?”

“No, no. I mean an old space movie. I’m something of a buff of pre-spaceflight cinema. A young actress called Jane Fonda …” Eugene clearly had no idea what he was talking about. “Never mind.”

Mikhail made his way to the dome’s small shower cubicle, stripped off the last of his clothing, and stood under a jet. The water emerged slowly, in big shimmering low-gravity droplets that fell with magical slowness to the floor, where suction pumps drew in every last precious molecule. Mikhail lifted his face to the stream, trying to calm himself.

Thales said gently, “I’ve brewed some coffee, Mikhail.”

“Thales, that was thoughtful.”

“Everything is under control.”

“Thank you …” Sometimes it really was as if Thales knew Mikhail’s moods.

Thales was actually a less sophisticated clone of Aristotle, who was an intelligence emergent from a hundred billion Earth-side computers of all sizes and the networks that linked them. A remote descendant of the search engines of the late twentieth century, Aristotle had become a great electronic mind whose thoughts crackled like lightning across the wired-up face of the Earth; for years he had been a constant companion to all humankind.

When humans had begun their permanent occupation of the Moon at Clavius Base, it had been inconceivable that they should not take Aristotle with them. But it takes light more than a second to travel from Earth to the Moon, and in an environment where death lurks a single error away, such delays were unacceptably long. So Thales had been created, a lunar copy of Aristotle. Thales was updated continually from Aristotle’s great memory stores—but he was necessarily simpler than his parent, for the electronic nervous system laid across the Moon was still rudimentary compared to the Earth’s.