“I noticed it today.”

She ran her finger over the balcony rail; the pad of her finger came away pink with grime. “The cleaning machines polished this only this morning.” She rubbed her fingers together, and the dry dust trickled to the floor. “There it is,” she said. “All those golf courses and holiday homes, and the salt-resistant rice and alfalfa and corn, all blown up into the air… Hush.” She raised a finger and peered into the dark.

I heard a rustling, coming from the alley below me. “What is it? A mouse, a rat?”

“Possibly. Though there isn’t much for them to eat anymore. It may be a robot, another of our guardian-angel machines, earnestly keeping the streets safe for old folk like me. I sometimes wonder — I’m told that the machines are as smart as dogs, or even some cats. When they have run out of vermin to eliminate, what will they do for sport? Will they turn on each other?…”

“Why is Spain so empty? What caused this depopulation?” I was faintly ashamed of my ignorance.

“The drought hasn’t helped,” Rosa said. “But the change has come from humanity, Michael, from inside us.”

Some time around the turn of the century, people all over the world just stopped having so many children. For a while the effect was masked; the end of the last century saw the biggest population bulge in human history, and as that vast cadre grew to childbearing age they flooded the world with yet more kids. But the bulge soon worked its way through the demographics, and the decline cut in.

Rosa said, “In Spain, the government became alarmed. It was thought at first that it was simply a choice of women taking control of their own bodies, on a mass scale perhaps for the first time in history. Spain, along with other countries, put in place more civilized child-care facilities — robots helped with that. More subtly, they tried to renegotiate gender roles, the unspoken contract between men and women. I watched all this from outside, of course. Quite a spectacle! Some of this social engineering worked, for example in the United States. But not in Spain, Italy, Greece, the more conservative, patriarchal countries. There, traditions are too deeply rooted to be shifted, even in the face of population collapse.

“But I think it’s all a lot deeper than a simple matter of stay-at-home fathers and day-care nurseries — don’t you? After all profound instincts are being defied here: the instinct to propagate the tribe, to fill the world with your brood, all the antique Iron Age drives that have enabled us to cover the planet. But now some other, more mysterious motivation is taking hold. Once people came here in great waves, the Romans and the Visigoths, the Moors and the Christians. And now they are leaving again — not going anywhere, just disappearing into lost potentialities. And when they’ve gone, there will be nothing but this aching emptiness. But it feels right. Don’t you think? It suits the times.”

“I’m surprised you’re happy to live alone like this.”

“At my age, you mean? Oh, I’m safe enough. I’m surrounded by machines, as we all are. Pointlessly intelligent, all of them. Machine sentience is now omniscient and omnipresent, just as we once imagined God to be — ha! I am sure they would not let me come to any harm.”

“What about crime?”

“I have no fear of that. Criminals prefer crowds, too. If I ever really feel I need people, I go to the more popular parts of town — El Arenal by the river, where the Plaza de Toros still stages fights between men and robot bulls, or Santa Cruz, the old Jewish quarter. And that is where the criminals go, too. And the crows and the rats…”

“But you prefer to stay here,” I said. “Away from the lights, the people.”

“I go where they need me,” she said. “But, yes, I prefer the silence. Sometimes you can feel it rise up around you, the emptiness, coming out of a thousand abandoned buildings, a million rooms empty of everything but garbage. I feel as if I’m in a tiny lifeboat, adrift in emptiness.”

“And you like to feel that way?”

“Where I grew up was rather different,” she said. “Somewhat crowded. Perhaps, late in life, I am enjoying the contrast.”

“Aunt Rosa, I think you spend too much time on your own.”

That won me a laugh. “Perhaps I do. Am I morbid, do you think? But I still have work to do here. You asked me about experiences beyond the natural…”

She told me a story.

She said that the city authorities were working their way through the depopulated districts, trying to make them safe. There was some demolition, but usually, more wistfully, what was called “mothballing,” as buildings were secured and sealed against the day when the people would return. And sometimes, in this patient cleaning-out, they found things that induced the firefighters or police officers or environment managers to call on the services of a priest like Rosa.

“In one case, as they approached a ruined old house, the workers thought they heard children singing, in harmony, like a school choir. But there were no children there. Then they found a cellar. It turned out that it had been used by a man who had taken children over a period of years. You don’t need to know the details. His crimes had never been discovered, not until now.

“The workers would not, could not enter that cellar. It wasn’t because of rot or decay or the danger of disease; their equipment would take care of that. But there was a deeper blight which they hoped I would confront, with my prayers.” She paused. Her small, closed-in face was quite unreadable now. “Have you ever been in the presence of evil, Michael?”

“I don’t think so—”

“You would know. In fiction, evil is portrayed as stylish, clever. The devil is a gentleman! But in fact evil is banal. In that cellar, the dirt, the blood, the bits of hair and clothing, even the scattered toys — it was nauseating, literally revolting, in a way a place of animals could never be.” She turned to me; her body stayed motionless while her head swiveled like an owl’s. “Your ghost. Your Morag. Is she evil, Michael?”

“No,” I said with certainty. “Whatever it is, she’s not that.”

She seemed to relax, subtly. “Good. At least we will not have to face that. Then we must seek out another explanation, a different interpretation. Perhaps you are a necromancer, Michael, in this capital city of necromancy; perhaps you are a man who speaks to ghosts to discern the future — what do you think?”

I thought I needed some more of that seawater wine.

Rosa had promised me that the next day she would take me to see the sights of Seville. We would climb La Giralda, a Moorish tower stranded in the middle of a Gothic Christian cathedral, and view the city. Or, better still, perhaps we would ride up the Sundial, the symbol of Spain’s number one export industry, electrical power. I thought it was interesting that Rosa’s ideas for a day out were all about going to high places. She sought out isolation and height, a contrast, it seemed, to her strange early life, which, as far as I could make out, had been in conditions of crowding, and deep underground.

I looked forward to seeing the Sundial, though. It was a solar-power tower a kilometer tall, rising from gleaming hectares of solar-cell farms, a modern wonder. Air heated at its base rose up through the tower and drove turbines. It was a simple design, if horribly inefficient — but who cared about efficiency when the sunlight was to be had for free?

But in the end we didn’t go anywhere, for the next day was a “dust day.”

I was woken by a rumble of traffic that wouldn’t have seemed unusual save that it was here. It wasn’t long after dawn. Looking out through the closed balcony windows I saw robot water lorries rolling down the street, spraying water over the street surface. They were broadcasting warnings in precise, clipped Spanish. In the middle distance the whole skyline was obscured by an orange-red haze, and the rising sun was a pale disc that threw only faint shadows on the empty road surface. We would likely be stuck indoors for the day, Rosa said.