Billy Harper was cleaning windows on the fortieth floor of the John Hancock Center when it started to snow. The wind was cold and sharp, cutting through his coat like a knife. His fingers were numb inside his gloves, and the soapy water in his bucket was freezing into tiny crystals that floated on the surface like sugar.

He was twenty-six, from a small town in Kansas where the wind was also cold and sharp, but at least it didn't come from forty stories up. He had come to Chicago two years ago because his mother was sick and he needed money. The cleaning job paid enough to send money home, not enough to keep her alive, but enough to try.

His coworker Ron Miller was cleaning the window next to him. Ron was about forty-five, with a paunch and a face that was always red, like he had been crying or drinking or both. Probably both.

"You're slow today," Ron said.

"I'm cold," Billy replied.

"Are you? Or are you paid to preserve? There's a difference."

Billy didn't understand what Ron meant, but he kept it in mind.

Ron used to be an engineer. He had worked on a project called the Solar Sail Energy Plan, which was supposed to use sunlight to generate electricity. The plan had been abandoned by the government, and Ron had been left with nothing. His wife had left him, his house had been foreclosed, and he had ended up cleaning windows.

"I used to build things," Ron said one day, during a break. "Real things. Machines. Engines. Things that worked."

"Now you clean glass," Billy said.

"Now I clean glass. There's a difference."

Billy ate his sandwich and looked out at the city. Chicago was gray and flat, like everything else in Illinois. The buildings were tall but ugly, like boxes stacked on top of each other. The sky was the color of dirty dishwater.

"Do you miss it?" Billy asked. "Building things?"

Ron was silent for a long time. "I miss the certainty. When you build something, you know it will work. You calculate the numbers, you test the materials, you build it, and it works. Or it doesn't. But you know why. With the solar sail, I knew it would work. I knew it. But the government said no. Said it wasn't profitable. Said nobody cared about energy from the sun."

"So you kept cleaning windows."

"So I kept cleaning windows."

The work took eight hours. Billy cleaned the windows, wiped the edges, filled his bucket. He did it every day, for two years. He cleaned windows in the rain and the snow and the heat and the cold. He cleaned windows until his hands were calloused and his back was bent and his eyes were tired.

Ron died in his apartment. The coroner said alcohol poisoning. Billy went to the funeral, but there were only three people there: Billy, the priest, and a woman who said she had been Ron's wife but didn't look like she wanted to be there.

Billy went back to cleaning windows. He cleaned them every day, for three more years. He cleaned them on the John Hancock Center, on the Sears Tower, on the Aon Center. He cleaned them in the rain and the snow and the heat and the cold. He cleaned them until his hands were calloused and his back was bent and his eyes were tired.

He never talked about Ron again. He never talked about the solar sail. He just cleaned windows, and sent money home, and waited for his mother to die.

She did. Three years later. Billy came home to Kansas, buried her in the cemetery next to the church, and went back to Chicago.

He kept cleaning windows. He kept sending money home. He kept waiting for something to change.

It never did.

The solar sail project was abandoned in 1978. The government said it wasn't profitable. The scientists said it would work. Nobody listened.

Billy cleaned windows until he was too old to climb the scaffolding. Then he cleaned windows from the ground, using a long pole with a squeegee on the end. He cleaned windows until his hands were too shaky to hold the pole. Then he stopped cleaning windows.

He sat on his porch and watched the sun go down. He thought about the solar sail, and the certainty of numbers, and the way equations resolved themselves into answers.

He thought about Ron.

And he thought about the sun, and how it came up every morning, and how it sent light to the earth, and how nobody cared.