“Most people have come to the same conclusion,” Doob said. “A pool of promising candidates is identified and then the choice is made from among them by some process which might be random—just so no one person carries the entire responsibility.”

“When you are a king you sometimes have such responsibilities whether you want them or not. In this case, though, I was able to involve some of the lamas. There are precedents for such a selection procedure in the way that certain reincarnate lamas are identified—the drawing of lots from an urn is sometimes used.”

Tav couldn’t resist asking from the backseat: “What does the doctrine of reincarnation have to say about the situation we are faced with now?”

The king smiled. “Mr. Prowse, this is only a journey of ten kilometers. I am taking it slow. If we had a road trip ahead of us of ten thousand kilometers—an enjoyable thought—I might be able to impart enough information to you about what reincarnation means to my people that we would be able to have an intelligent conversation about it.”

“Fair enough. Sorry,” Tav said, glancing up from the screen of his phone when his brain detected a pause in the king’s speech. “You have to understand, my job is to communicate with geeks. People who like math. So I was trying to imagine—”

“When seven billion die, and only some thousands remain, where do the seven billion souls go?”

“Yes.”

They turned off what Doob guessed was the main road and onto a fork that wound through a wooded hamlet above the river. This hooked onto a bridge that took them across a fast-running, cold-looking stream, green and milky with rock flour carried down from melting glaciers thousands of meters above their heads. Doob still couldn’t get over the fact that in a little more than a year those glaciers would be gone, the rock beneath them exposed for the first time in millions of years, and no scientist would be there to record it.

“We don’t believe in anything as simple as metempsychosis—the movement of an individual soul from one body to another. That’s not what we mean by reincarnation at all.”

“What do you believe in, then?” Doob asked. Tav had lost interest and was belaboring his phone with his thumbs.

“A better analogy might be to a burned-down stump being used to ignite a new candle. But I won’t be able to give you a satisfactory answer, Dr. Harris. The teachings are esoteric—deliberately hidden from the uninitiated, specifically to prevent false interpretations. How an enlightened lama would think about the question of the seven billion is as far beyond my comprehension as are the quantum gravity theories that you study in your work.”

On this side of the river the ground rose almost vertically. The mountain barrier was cleft by a steep-sided valley that zigzagged up and away from them; the road leaped up into it and switchbacked up a stone cliff, fringed here and there with clusters of hardy evergreens that had found toeholds in crevices. Tendrils and torn veils of mist drifted across the face of the rock, providing occasional glimpses of a white tower, high above them, that had somehow been constructed on the precipice. It was one of those buildings, like some monasteries in Greece and Spain, whose whole point was to proclaim to those below, “This is how far we will go to achieve separation from the world.”

They drove up a road between long green terraces until the ground became too steep for wheels, and then the king stopped the Land Rover and set the brake. “How’s your cardio?”

“Could be better,” Doob said, “but I don’t have a heart condition, or anything like that.”

“We are at about three thousand meters above sea level. You are welcome to await the chosen ones here in my vehicle, or—”

“I could use a walk, thanks,” Doob said, and glanced back at Mario, who shrugged philosophically, and at Tavistock Prowse, who appeared to be biting his tongue.

As they hiked up the trail, followed at a respectful distance by an entourage of lamas, children, photographers, and officers of the Bhutanese military, the king told Doob that the place they were going was called the Tiger’s Nest and that it was one of the most sacred sites in their religion, being the spot where Guru Rinpoche, the Second Buddha, had, in the eighth century, flown in from Tibet on the back of a tiger. Later a temple complex had been built around the caves where Padmasambhava (for apparently this was an alternate name for the same personage) had lingered to meditate.

Doob pleased himself by suppressing the urge to point out to the king that tigers were not capable of flight. This was only partly because he was gasping for air. He did not really care about the plausibility of the story, given the astonishing beauty of the place through which they were hiking. It was one thing to be fed a line of religious hokum in a desert hellhole that had nothing to recommend it as a site for tourism. But in order to go for a few hours’ walk with a king in Shangri-La, he would put up with any amount of fairy tales and metaphysical ramblings.

Small temples and devotional sites emerged from the mist every few minutes. They stopped part of the way up to enjoy a serving of chai in a little café with a fine view of the Tiger’s Nest. Tav, at the end of his rope physically, announced he would go no farther. Doob, Mario, and the king pushed on along the increasingly precarious walkway to the gates of the monastery itself. This, the king had already informed Doob, was off-limits, and in any case would have made a poor showing as a site for a ceremony, being rather cramped, dark, mazy, and ancient. Crag-dwelling hermit monks didn’t go in much for grand ceremonial courtyards.

Instead there was a sort of wide spot in the ledge just before the entrance to the white temple. Waiting there were the two Arkers, a boy and a girl, both in their early twenties, clad in what Doob assumed was traditional costume: For the boy, a robe that stopped at his knees, with a large white scarf over his shoulder and crossed to his hip. For the girl, a bolt of colorfully woven cloth, wrapped around her waist and falling to her ankles as a sort of columnar skirt, with a yellow silk jacket above that, draped with many necklaces of turquoise and other colorful stones.

Had she been here, Amelia, in a single glance, would have noticed a hundred details about the weaving, the embroidery, the jewelry, the drape of the fabrics, the choice of colors. She would have charmed the king right out of his saffron scarf. She would have climbed out of the Land Rover back in Paro and made friends with the soccer-playing boys. Amelia, not Doob, was the person who ought to be doing all of this.

But Amelia wasn’t going to the Cloud Ark and Doob was.

The boy and the girl—Dorji and Jigme, respectively—were backed up by some leathery oldsters in similar but simpler costumes, presumably their families, and several lamas. Prayer wheels were spinning, bells were chiming back inside the monastery, monks were chanting.

Everyone was crying.

They all bowed to their king.

Doob was glad Tav had not come this far.

Some kind of conversation took place in the local language. Doob didn’t even know what the name of that language was. Mario, oblivious to the emotional tenor of the proceedings, darted around snapping photographs, dropping to his knees or even throwing himself flat on the ground so that he could get mountain peaks or temple roofs in the backdrop of shots.

Doob, who had no idea what was going on, couldn’t take his eyes off the faces of the elders, who were doing their best to hold it together in the presence of their monarch but clearly suffering through ruinous emotional pain as they prepared to say goodbye to Dorji and Jigme forever. It was almost worse than watching your kid die, Doob thought. Then there was finality, certainty, a grave site to visit. Whereas these two were just going to hike off into the mist. A thunder of helicopter blades would announce their departure, and after that the family members would get vague assurances that Dorji and Jigme were going into space to carry forward the cultural legacy of Bhutan. Assurances that, Doob was pretty sure, were going to be fundamentally dishonest. These people were going to go to their deaths in fifteen months consoling themselves with that belief.