Inside, old photos line the walls, showing great expanses of scaffolded concrete and bushy-browed men in overalls standing inside huge turbines. The tourists are being shuffled into a small theater. Turtle tugs her in for the show, but Taylor regrets it as soon as the projector rolls. The film describes the amazing achievement of a dam that tamed the Colorado River. In the old days it ran wild, flooding out everyone downstream, burying their crops in mud. “There was only one solution—the dam!” exclaims the narrator, who reminds Taylor of a boy in a high school play, drumming up self-importance to conquer embarrassment. Mr. Hoover’s engineers prevailed in the end, providing Arizona with irrigation and L.A. with electricity and the Mexicans with the leftover salty trickle.

“Another solution is they didn’t need to grow their cotton right on the riverbank,” Taylor points out.

“Mom!” hisses Turtle. At home Turtle whines when Taylor talks back to the TV. Jax sides with Turtle on the television subject, citing the importance of fantasy. Taylor sides with her mother, who claims over the phone that TV has super-natural powers over her husband. “Just don’t believe everything on there is true,” Taylor warns often, but she knows this war is a lost cause in general. As far as her daughter is concerned, Mutant Ninja Turtles live in the sewers and that is that.

Outside the museum, a foil gum wrapper skates along the sidewalk on a surprise gust of wind. A herd of paper cups and soda straws rolls eastward in unison. Lucky Buster sits on the ramparts of the Hoover Dam, trying to figure out how to save the day. People will throw anything in the world on the ground, or even in the water. Like pennies. They end up down there with the catfish. There could be a million dollars at the bottom of the lake right now, but everybody thinks there’s just one red cent—the one they threw.

Lucky sits very still. He has his eye on a bright red soda-pop can. His friend Otis is an engineer for the Southern Pacific, and he’s warned Lucky about pop cans. They catch the sun just right and they’ll look like a red signal flare on the tracks. When you see that, you’ve got to stop the whole train, and then it turns out it’s just a pop can. Bad news.

The people are all up above him. One girl is looking. Her round face like a sweet brown pie can see him over the wall.

He waves, but she bobs behind the mother and they go away.

Nobody else is looking. He could go down there now. The water is too close, though, and scares him: water is black, blue, pink, every color. It gets in your eyes there’s so much light. He looks away at the nicer camel hump desert. Now: go.

Lucky drops down and scoots along the gray wall that runs along the edge. One side is water, fish-colored; on the other side you fall into the hole. He is as careful as the circus girls in silver bathing suits on TV, walking on wires. One foot, another foot.

A white bird with scabbed yellow feet lands in front of Lucky. “Ssss,” he says to the bird, shaking his hands at it.

The bird walks away fast, one spread foot and then the other one. Lucky is two steps away from the pop can. Now one step away. Now he’s got it.

The bird turns its head and looks straight at Lucky with a mean eye.

The sun has dropped into the Nevada hills and rung up a sunset the color of cherries and lemons. Turtle and Taylor take one last stroll across Mr. Hoover’s concrete dream.

Turtle is holding on so tightly that Taylor’s knuckles ache.

Their hypochondriac friend Lou Ann has warned Taylor about arthritis, but this snap-jawed grip is a principle of their relationship; it won Turtle a nickname, and then a mother.

She hasn’t deliberately let go of Taylor since they met.

The water in the shadow of the dam is musky green and captivating to Turtle. She yanks on Taylor’s fingers to point out huge catfish moving in moss-colored darkness. Taylor doesn’t really look. She’s trying to take in the whole of Lake Mead, the great depth and weight of water that formerly ran free and made life miserable for the downstream farmers. It stretches far back into the brown hills, but there is no veget-ation along the water’s edge, just one surface meeting another, a counterfeit lake in the desert that can’t claim its own shoreline. In the distance someone is riding a kind of small water vehicle that seems pesty and loud for its size, like a mosquito.

Storm clouds with high pompadours have congregated on the western horizon, offering the hope of cooler weather, but only the hope. The Dodge when they get back to it is firecracker hot and stinks of melted plastic upholstery. Taylor opens both front doors and tries to fan cooler air onto the seat. The ice-cream cone she bought Turtle was a mistake, she sees, but she’s not an overly meticulous parent. She’s had to learn motherhood on a wing and a prayer in the last three years, and right now her main philosophy is that everything truly important is washable.