What is the basic storyline of Specimen Days?

Specimen Days by Michael Cunningham is classified as a novel, but it contains three separate stories. The stories take place in New York City at different times—past, present, and future. They feature the same characters in different guises, and they share similar themes.
The first story, “In the Machine,” takes place in the past. It is the story of Lucas, a young boy who works in a factory during the Industrial Revolution and who believes that the machines in the factory are haunted by ghosts that lure people into the machines to die. He believes his brother Simon died that way, and he attempts to warn his brother’s girlfriend Catherine that she is in danger of dying the same way.
The second story, “The Children’s Crusade,” is the story of a group of teenage suicide bombers in post-9/11 New York who bomb victims at random. It is also the story of Cat, a police psychologist who discovers the bombers and who bonds with one of them, Luke, because he reminds her of her son. Cat is in love with a man named Simon.
The third story, “Like Beauty,” takes place in the future, after nuclear war has destroyed much of the world, and it features an android named Simon, a reptilian woman named Catareen, and a boy named Luke. They travel by hovercraft to Denver to escape government persecution.
The characters of Luke, Simon, and Cat appear in all three stories and share similar traits, though the stories take place in different historical eras. In all three stories, the characters’ fascination with and recital of Walt Whitman poems plays a role in the plot.