“You have to wonder about the Chinese alchemists who invented gunpowder,” Oppy said. “When they were on the verge of discovery, were they fortunate enough to have a night as quiet and beautiful as this? Perhaps the emperor of China had horsemen searching for them, just as jeeps are searching for us. Perhaps we’ll meet them.”

“What do you mean?” Groves asked.

“Einstein says time bends around the universe in a curving line. On that line you can go backwards or forwards. We’ll never find this same Stallion Gate here again, but we can always find it on some cusp of time. If we could do that, we could meet those Chinese horsemen, too.”

“I’ll tell you about going back to the past,” Groves snorted, and filled his hand with caramels from his pocket. “The bitterest day of my life was when I was ordered to rescue this project. I had just been offered my first combat command the week before. A soldier wants to see combat. My father was an Army chaplain, and even he saw combat. There I was, Army born and bred, ordered to spend history’s greatest war at home overseeing a bunch of scientific prima donnas who, as far as I could tell, had sold the President a bill of goods.” He popped a caramel into his mouth and ruminated. “Well, I don’t run phony projects that don’t show results. A lot of scientists and so-called geniuses tried to sell me a bill of goods on how to make this atomic bomb. The greatest American physicist is E. O. Lawrence. I like Lawrence. He put the cyclotron on the map and he won the Nobel Prize, but he’s hardly produced a speck of uranium. Nevertheless, I will make this project a success. It’s largely a matter of plumbing, albeit complicated.” Oppy’s eyes glittered with amusement. Groves wiped his fingers in the snow. “In fact, I have never been more positive of success than I am at this very moment, at this very place.”

“This will be your monument,” Oppy said.

“Monument?” Groves sighed. “After I built the Pentagon, I calculated that in my career I had moved enough earth and laid enough cement to build the Pyramids of Cheops two hundred times over.”

“This is a different kind of pyramid,” Oppy suggested. “It has different blocks—some steel, some gold, some of water, some so radioactive you can’t touch them or even come close to them—and the pyramid must be built according to a blueprint no one has ever seen.”

“Let me tell you the kind of monument I want,” Groves said. “I’ve seen the estimates of the casualties we’re going to suffer in the invasion of Germany and Japan. I wouldn’t mind a monument of a million American lives saved.”

Groves’ sincerity was ponderous and real and demanded silence. Embers slipped and rose.