Eventually Sonia timed us out. We were getting too deep into specifics, she said.

“OK,” Shelley conceded. “But we must get in touch with some of those geoengineering groups, whatever we decide to do. They have got to have experience of these megaprojects we can tap into.”

Tom was shaking his head, in a world-weary way I’d seen too often as he was growing up. “Geoengineering. Terraforming. Wet dreams.”

I snapped, “What use is it to sneer, Tom? And besides it was you who suggested we cool the poles.”

“I didn’t say cool, ” he said. “I said refrigerate. ”

Shelley jumped in between us, damping down the fire before it started. “You’re quite right, Tom.” She thought it over. “A refrigerator is a machine for extracting heat from a volume. So how does it work? You pass your working fluid, your refrigerant — ammonia, say — around the volume you want to chill. The refrigerant is vaporized with heat from your target volume, so extracting the energy. As a gas the refrigerant is passed to a condenser, where it is returned to liquid form and so gives up that heat. And then the liquid is pumped around the loop again to suck more heat out.”

Sonia made notes, but she looked dubious. “How could you refrigerate the hydrate deposits? They are buried deep, and they cover millions of square kilometers.”

“It needn’t be so difficult,” I said, thinking fast. “You’d pass a network of pipes into the substance of the hydrate deposits themselves. It wouldn’t take long to build up a functioning network.” I sketched rapidly, producing a sketch that looked a little like a road network, with big arterial routes and smaller side roads branching off. “Your working fluid needn’t be ammonia, of course. In these volumes it probably couldn’t be. Liquid nitrogen, perhaps — you could just draw down the nitrogen from the air…”

Tom was shaking his head again, and I was on the point of snapping back at him, and I knew that despite all Sonia’s hard work we were falling into the elephant traps of our relationship.

But Sonia and Shelley seemed to come to the same conclusion simultaneously. We needed a break. They both stood up. “Lunchtime,” Shelley said. “Michael, you’re the cook.”

“Fine,” I said with bad grace. Tom clambered out of his chair looking as grumpy as I felt.

Sonia made one last note. “Refrigerate.Hold that thought.”

Lunch was a buffet, plastic-wrapped plates of stuff I’d prepared earlier in the day: smoked snake meat, a green salad with big, bright leaves of out-of-season gen-enged lettuce. We filled our plates and our glasses. I had some of those little clip-on drink holders that you fix to the side of your plate, and I let my guests wander around the house.

Shelley said to me around a mouthful of snake meat, “It’s going well, don’t you think?”

“The session? We’re coming up with some ideas, I guess. I think you’re right, we ought to contact those geoengineers if we’re going to start treading on their turf—”

She shook her head. “Not that. The important stuff. You and Tom. You seem to be getting on OK. The real reason, the only reason you’re interested in saving the world is because it gives you something to talk to your son about. Isn’t that true?”

Just as George had said, I remembered. “I guess so. But why else would anybody do it? Anyhow we’re both on our best behavior with you two around.”

“Sonia is quite a find, isn’t she?”

“You like her?”

“I think she’s terrific,” Shelley said. “Smart, obviously competent, healthy — what more could you want? She’ll be good for Tom. How close do you think they are?”

“I can’t tell. I never could…” I’ve always had a complicated view of relationships — either subtle or confused, depending on your point of view. It seems to me that there is a whole spectrum of possibilities between the poles of platonic and lover, whole levels of intimacy, sharing, degrees of distance. When I was younger I always enjoyed the early days of a new romance as you both reach out to explore, trying to understand what you had, where on that spectrum of possibilities you sat.

I tried to explain this to Shelley.

“ ‘A spectrum of relationship types,’ ” she said. “Even when you talk about love you sound like an engineer.”

“Is that a bad thing?”

“Not necessarily.”

“Looking from the outside Tom seems to be just the same,” I said. “Maybe he’s at the early stages still with this Sonia, you think?”

“Oh, I think they’ve gone further than that.”

“How do you know?”

“The way they look at each other — or rather the way they don’t. The way they sit together. They’re aware of each other, but in an accustomed way, they don’t need to check. They’re used to each other, Michael.”

Now that I thought it over, I saw she was right. “I hope they’ll be happy.”

“Oh, I think they will be. So where do you think we are on your spectrum?”

I was taken aback; I’d never thought of Shelley that way.

She squeezed my arm. “I didn’t mean to frighten you. Don’t worry, Michael. I do understand, you know.”

“You do?”

“Sure. Because for you, the spectrum isn’t there anymore, is it? For you there is only Morag, and that’s all there can ever be. Morag, wrapped in a rainbow cloak. But I’m here anyhow.”

“I—”

“You don’t know what to say? So don’t say anything.”

Tom, followed by Sonia, came walking through from the lounge. His face was ominously hard. “Dad, you had a message. I took it for you. Sorry, I obviously wasn’t meant to hear it.” His tone dripped with insolence, or contempt.

“What message?”

“From Rosa in Seville. My aunt,” he explained to Shelley and Sonia. “Another bat in the family belfry. She said your immigration checks have been completed, and she’s been passed as a suitable personal mentor for you while you’re in Spain. Oh, and she said she looks forward to ‘swapping ghost stories’ with you.” His anger was obvious, cold.

Shelley took a step back from me and sighed. “Oh, Michael.” And Sonia avoided my eyes. She was a sane person giving a nut some space. My embarrassment deepened.

“I thought you were done with this stuff, Dad,” Tom said bitterly. “Didn’t we have a deal?”

“I’m sorry.”

“But you’re going over there even so.”

“I have to.”

Shelley sighed again. “I thought we had you back, too, Michael. But you were fooling us, weren’t you?” Somehow her disappointment in me hurt more than Tom’s reaction. She dumped her plate on the table. “OK, that’s enough bullshit — and enough of this rabbit food, thanks all the same, Michael. Let’s get back to work.” She put an arm around Tom’s shoulders. “I want to follow up this idea of yours. Refrigeration…”

She led him into the lounge, and Sonia followed, without so much as glancing at me. I was left alone in the kitchen.

I took a few minutes scraping garbage into the recycler and stacking dishes, time I needed to calm down. I found myself trembling. It might have been easier if Tom had actually screamed at me.

Then I followed them all back into the lounge, where they had started to work again, filling pages and screens with sketches and notes, as, slowly, an inchoate dream of a refrigerator system big enough to encompass the pole of a planet took shape. But for the rest of the day I felt excluded, as if I had committed an awful transgression, a ghost in my own home.

For the third part of her training, the Implication of Emergent Consciousness, Alia was to be brought to a world at the heart of the Galaxy. She was dismayed at the thought of being taken to yet another dull mass of pointless geological stasis. And like so many others this world seemed to have no name, only a number assigned to it in the vast, growing catalog of the Commonwealth.

But this, Reath said, was a world of Transcendents.