The sound was a whizz followed by a rapid series of staccato explosions. It could be written as: ZZIKKH where the entire sound takes about a quarter of a second. None of us really saw anything. Casimir was already running toward the momentum absorber. When we got there, we saw that the first five layers of plywood had perfectly clean round holes punched through them, two more had messy holes, and the next layer had buckled, the brass cylinder wedged in place at its bottom. Casimir pulled out the payload with tongs and dropped it into an asbestos mitt he had donned. "It's pretty hot after all those collisions," he explained.

Everyone but Casimir was electrified. Even the Neutrino observers, who had seen it before, were awed, and laughed hysterically from time to time. Sarah looked as though whatever distrust she had ever had in technology had been dramatically confirmed. I stared at Casimir, realizing how smart he was. Virgil left, smiling. Krupp's little friend paced between mass driver and target, hands clasped behind back, a wide smile nestled in his silver-brown beard, while Krupp himself was astonished.

"Jesus H. Christ!" he yelled, fingering the holes. "That is the damnedest thing I've ever seen. Good lord, boy, how did you make this?"

Casimir seemed at a loss. "It's all done from Sharon's plans," he said blankly. "He did all the magnetic fieldwork. I just plugged in the arithmetic. The rest of it was machine-shop work. Nothing complicated about the machine."

"Does it have to be this powerful?" I said. "Don't get me wrong. I'm impressed as hell. Wouldn't it have been a little easier to make a slower one?"

"Well, sure, but not as useful," said Casimir. "The technical challenges only show up when you make it fast enough to be used for its practical purpose– which is to shoot payloads of ore and minerals from the lunar surface to an orbital processing station. For a low-velocity one we could've used air cushions instead of magnetic fields to float the bucket but there's no challenge in that."

"What's the muzzle velocity?" asked Krupp's guest, who had appeared next to me. He spoke quietly and quickly in an Australian accent. When I looked down at him, I realized he was Oswald Heimlich, Chairman of the Board of Trustees of American Megaversity and one of the richest men in the city – the founder of Heimlich Freedom Industries a huge defense contractor. Casimir obviously didn't know who he was.

"The final velocity of the bucket is one hundred meters per second, or about two hundred twenty miles per hour."

"And how could you boost that?"

"Boost it?" Casimir looked at him, startled. "Well, for more velocity you could build another just like this– "

"Yes, and put them together. I know. They're interconnectible. But how could you increase the acceleration of this device?"

"Well, that gets you into some big technical problems. You'd need expensive electronic gear with the ability to kick out huge pulses of power very quickly. Giant capacitors could do it, or a specialized power supply."

Heimlich followed all this, nodding incessantly. "Or a generator that gets its power from a controlled explosion."

Casimir smiled. "It's funny you should mention that. Some people are speculating about building small portable mass drivers with exactly that type of power supply– a chemical explosion– and using them to throw explosive shells and so on. That's what is called– "

"A railgun. Precisely."

Things began to fall into place for Casimir. "Oh. I see. So you want to know if I could build– basically a railgun."

"Sure. Sure," said Heimlich in an aggressive, glinting voice. "What's research without practical applications?" The question hung in the air.

Krupp took over, sounding much calmer. "You see, Casimir, in order to continue with this research– and you are off to an exceptionally fine start– you will need outside funding on a larger scale. Now, as good an idea as lunar mining is, no one is ever going to fund that kind of research. But railguns– whether you like it or not, they have very immediate significance that can really pull in the grants. I'm merely pointing out that in today's climate relating your work to defense is the best way to obtain funding. And I imagine that if you wanted to set up a specialized lab here to advance this kind of work, you might be able to get all the funding you'd want."

Casimir looked down at the shattered plywood in consternation. "I don't need an answer now. But give it some careful thought, son. There's no reason for you to be stuck in silly-ass classes if you can do this kind of work. Call me anytime you like." He shook Casimir's hand, Heimlich made a brief smiling spastic bow, and they walked out together.

Sarah quit the Presidency of the Student Government on the first of January. At the mass-driver demonstration, S. S. Krupp had simply ignored her, which was fine by Sarah as she had no desire to give the man a point-by-point explanation.

As for the death of Tiny, here the other shoe never dropped, though Sarah and Hyacinth kept waiting. His body was in especially poor condition when found, and the bullet holes might not have been detected even if someone had thought to look for them. The City police made a rare Plex visit and looked at the broken window and the electrocuted man on the floor, but apparently the Terrorists had cleaned up any blood or other evidence of conflict; in short, they made it all look like a completely deranged drunken fuck-up, an archetype familiar to the City cops.

The Terrorists wanted their own revenge. None of them had a coherent idea of what had happened. Even the two surviving witnesses had dim, traumatized memories of the event and could only say it had something to do with a woman dressed as a clown. As soon as I heard that the Terrorists were looking for someone called Clown Woman, I invited her over and we had a chat. I knew what her costume had been. Though she understood why I was curious, she suddenly adopted a sad, cold reserve I had never seen in her before.

"Some really terrible things happened that night. But I'm I Hyacinth is safe– okay? And we've been making plans to stay that way."

"Fine. I just– "

"I know. I'd love to tell you more. I'm dying to. But I won't, because you have some official responsibilities and you're the kind of person who carries them out, and knowing anything would be a burden for you. You'd try to help– but that's something you can't do. Can you understand that?"

I was a little scared by her lone strength. More, I was stunned that she was protecting me. Finally I shrugged and said, "Sounds as though you know what you're doing," because that was how it sounded.

"This has a lot to do with your resigning the Presidency?" I continued. Sarah was a little annoyed by my diplomacy, for the same reason S. S. Krupp would have been.

"Bud, I don't need some terrific reason for resigning. If I'm spending time on a useless job I don't like, and I find there are better things to do with that time, then I ought to resign." I nodded contritely, and for the first time she was relaxed enough to laugh. On her way out she gave me a long platonic hug, and I still remember it when I feel in need of warmth.

They got the wading pool and the garden hose on a two-hour bus ride to a suburban K-Mart. Hyacinth inflated it in the middle of Sarah's room while Sarah ran the hose down the hall to the bathroom to pipe in hot water. Once the pool was acceptably full and foamy, they retrieved the hose, locked the door and sealed off all windows with newspaper and all cracks around the door with towels and tape. They lit a few candles but blew most of them out when their eyes adjusted. The magnum of champagne was buried in ice, the water was hot, the night was young. Hyacinth's .44 was very intrusive, and so Sarah filed it under G for Gun and they had a good laugh.