ALEC ASKED, LOOKING IN the rearview mirror at Dan, whose eyes were closed in a kind of nervous meditation. “I’m good,” Laura answered. Alec ignored her. He wasn’t concerned about Laura. She had the easy job. “Dan? Ready?” he asked again. “It’s time.” Dan didn’t meet Alec’s eyes, but opened the car door and stepped into the visitor parking lot of the Glen Canyon Dam. Their beat-up Chevy Bronco was one of only three vehicles there—the other two were desert-camouflaged Humvees. Alec smiled. Soon there would be at least fifty thousand dead. Probably more. Lake Powell, the enormous reservoir just upriver from the Grand Canyon, got three million visitors per year, and even though it was September now—not peak season—there had to still be at least fifty thousand people on the lake. Add to that anyone in the bottom of the Grand Canyon. All of the water from Lake Powell would scour the Grand Canyon and then pour into Lake Mead, overtopping the Hoover Dam and taking it out, too, in a violent flood.