It was like an explosion, rocking everything Susan and I had ever known.

The clock had started on that autumn day.

The countdown had begun.

I had only a year or so left to live.

11

Hollus and I went down into the Lower Rotunda each evening, after the museum closed to the public. As payment for what I’d let him see, he continued to present recreations of various periods from Beta Hydri III’s geologic past, and I recorded all of these on video.

Maybe it was because my own life was coming to an end, but after a while, I yearned to see something else. Hollus had mentioned the six worlds apparently abandoned by their inhabitants. I wanted to see them, see the most recent artifacts on these alien worlds — the last things the inhabitants had built before they disappeared.

What he showed me was amazing.

First was Epsilon Indi Prime. On its southern continent, there is a huge square, enclosed by walls. The walls are made of giant, roughly hewn granite blocks each more than 8 meters on a side. The area they enclose, almost 500 meters across, is filled with rubble: gargantuan, jagged hunks of broken concrete. Even if one could climb the walls, the vast field of rubble would be imposingly barren. No animal or vehicle could traverse it without great difficulty, and nothing could ever be made to grow there.

Then there’s Tau Ceti II. In the middle of a barren landscape, the long-gone inhabitants had made a disk of fused black stone more than 2,000 meters across and, judging by its edge, more than 5 meters thick. The black surface absorbs heat from its sun, making it incredibly hot; flesh would blister trying to walk across it, and the soles of shoes would melt.

The surface of Mu Cassiopeae A Prime reveals no sign of its former inhabitants; everything has been buried by 2.4 million years of erosion. But Hollus showed me a computer-generated model of what the starship Merelcas’s sensors had revealed beneath the layers of sediment: a vast plain filled with towering, twisted spires, spikes, and other jagged forms, and beneath that, a vault or chamber, forever hidden from view. That planet had once had a very large moon — proportionately, much larger than Luna is in relation to Earth — but it now sported a glorious system of rings instead. Hollus said they’d determined the ring system was also 2.4 million years old — in other words, it had come into existence at the same time the Cassiopeians had vanished.

I had him show me the rest of the planet. There were archipelagos in the seas — islands spread out like pearls on a string — and the eastern shoreline of the largest continent closely matched the western shoreline of the next largest: telltale signs of a world that had been undergoing plate tectonics.

“They blew up their own moon,” I said, surprising myself with the insight. “They wanted to put an end to its tidal forces churning their planet’s core; they wanted to shut off plate tectonics.”

“Why?” asked Hollus, sounding intrigued by my notion.

“To prevent the vault they’d built from ever being subducted,” I said. Continental drift causes crustal rocks to be recycled, with old ones pushed down into the mantle and new ones forming from magma welling up at sea-floor trenches.

“But we had assumed the vault was for the storage of nuclear waste,” said Hollus. “Subduction would actually be the best way to get rid of it.”

I nodded. The monuments he’d shown me here and on Tau Ceti II and Epsilon Indi Prime were indeed reminiscent of designs I’d seen proposed for nuclear-waste sites on Earth: artificial landscapes so foreboding that no one would ever dig there.

“Did you find any inscriptions or messages related to nuclear waste?” I said. The plans for Earth’s waste sites all involved symbolic communication indicating the sort of dangerous materials being stored, so that any future inhabitants of the area would understand what had been buried. The proposed iconography ranged from human faces showing expressions of illness or disgust, indicating that the area was poisonous, to diagrams using atomic numbers to note specifically what elements were interred.

“No,” said Hollus. “Nothing like that. Not in the most recent sites, at least — the ones that I have been showing you from just before the races disappeared.”

“Well, I suppose they could have wanted the sites to go undisturbed for millions of years — for so long that whatever intelligences that later discovered them might not even be of the same species as those who had buried the waste beneath the warning landscapes. It’s one thing to try to communicate the idea of poison or sickness to members of your own species — we humans associate closed eyes, frowning mouths, and protruding tongues with poisoning — but it might be quite another to try to do it across species boundaries, especially when you know nothing about the species that might succeed you.”

“You are not integrating,” said Hollus. “Most radioactive waste has a half-life of less than a hundred thousand years. By the time a new sapient species has emerged, there would be virtually nothing dangerous left.”

I frowned. “Still, they do look a lot like nuclear-waste storage sites. And, well, if the natives of the planets departed to go somewhere else, maybe they felt it was appropriate to bury their garbage before leaving.”

Hollus sounded dubious. “But why then would the Cassiopeians want to stop subduction? As I said, that is the best way to get rid of nuclear waste — even better than firing it off into space. If the spaceship you are using explodes, you can end up with nuclear contamination spread over half your world, but if the waste is carried down into the mantle, it is gone for good. That is, in fact, what my own race ended up doing with its nuclear waste.”

“Well, then, maybe they buried something else beneath those warning landscapes,” I said. “Something so dangerous, they wanted to make sure that it would never be uncovered, so that it could never come after them. Maybe the Cassiopeians were afraid if the vault was subducted, its walls would melt and whatever — whatever beast perhaps — they’d imprisoned within might escape. And then, all these races, even after burying whatever they were afraid of, left their homeworlds, putting as much distance as possible between themselves and whatever it was they’d left behind.”

“I’m thinking of going to church this Sunday,” Susan had said last October, shortly after our first appointment with Dr. Kohl.

We’d been sitting in our living room, me on the couch, she on the matching chair. I’d nodded. “You usually do.”

“I know, but — well, with everything that’s happened. With . . .”

“I’ll be all right,” I said.

“Are you sure?”

I nodded again. “You go to church every Sunday. That shouldn’t change. Dr. Kohl said we should try to keep our lives as normal as possible.”

I wasn’t sure what I’d do with the time — but I’d find plenty. At some point, I’d have to call my brother Bill in Vancouver and let him know what was happening. But Vancouver was three hours behind Toronto, and Bill didn’t get home from work until late. If I called in what was the early evening his time, I’d end up speaking to his new wife Marilyn — and she could talk your ear off. I wasn’t up for that. But Bill, and his kids from his previous marriage, were the only family I had; our parents had passed away a couple of years ago.

Susan was thinking; her lips were pursed. Her brown eyes briefly met mine, then looked at the floor. “You — you could come with me, if you want.”

I exhaled noisily. It had always been something of a sore point between us. Susan had gone to church regularly her whole life. She knew when she married me that that was not something I did. I spent my Sunday mornings surfing the web and watching This Week with Sam Donaldson and Cokie Roberts. I’d made it plain to her when we started dating that I wouldn’t be comfortable going to church. It would be too hypocritical, I said — an insult to those who believed.