Samantha was sitting on a lawn chair in her parents’ garage, smoking a joint, when she decided to run away. She had just graduated from high school, where she had few friends, and felt invisible. She went to class stoned and wrote suicidal poems about the shame of being molested by a family friend: “why try when there is no hope / for my dirty soul there is no soap.” The thought of remaining in her home town, in central Florida, made her feel ill. Reclining in her chair in the brightly lit garage, she closed her eyes and thought, Is this going to be my life?

Samantha had got A’s in high school and had planned to escape to college, until she realized she couldn’t afford it. The only other option, she decided, was to flee. She wanted to go to Manhattan, which she’d never visited, because it seemed like a good place to meet other lesbians. Samantha enjoyed reading about botany and had long assumed that, like some plants, she was asexual, a self-sustaining organism. She found it trivial and unbecoming when girls at school pined over their crushes. Then, at fifteen, she watched “Lara Croft: Tomb Raider” and was uncomfortably captivated by Angelina Jolie. Her English teacher at the time had the students spend five minutes every day on an exercise called Vomit, in which they wrote down every phrase that occurred to them. Their pens could not stop moving. “In my fifty-millionth Vomit, I spaced out and wrote, ‘I’m a lesbian and no one knows,’ ” she told me. “It was this crazy voice that knew.”

Throughout the summer of 2009, Samantha researched the logistics of being homeless in New York, reading all the articles she could find online, no matter how outdated. She learned that if she went to a homeless shelter before she was eighteen social workers would be required to contact her family. She wanted nothing to do with her parents, who, she believed, hadn’t taken her complaints of sexual abuse seriously; her mother suggested it was a hallucination. Samantha planned to live on the streets for several weeks, until her eighteenth birthday. Then she would begin the rest of her life: getting a job, finding an apartment, and saving for college.

In a purple spiral-bound notebook, she created a guide for life on the streets. She listed the locations of soup kitchens, public libraries, bottle-return vending machines, thrift stores, and public sports clubs, where she could slip in for free showers. Under the heading “known homeless encampments,” she wrote down all the parks, boardwalks, and tunnels where she could sleep and the subway line she’d take to get there. Her most detailed entry was a description of an abandoned train tunnel in Harlem and the name of a photographer who had taken pictures of the homeless people who lived in it. She hoped that if she mentioned the photographer’s name she would be “accepted by the underground society.”

On September 5, 2009, she bought a Greyhound bus ticket using the name Samantha Green. (She has asked me not to use her legal name.) Her parents were away for the day, visiting friends, and she told her thirteen-year-old brother that she was leaving for New York. He expressed concern about her being homeless, but she reassured him. “It’s kind of like camping,” she said. Her brother, who had always treated her with reverence, agreed not to tell her parents where she was going. He helped her break into her father’s safe so that she could take her birth certificate. Then he drove her to Walmart, where she bought a durable backpack, a roll of duct tape, protein bars, multivitamins, a box of garbage bags, a canteen, and a jar of peanut butter.

Samantha’s parents came home six hours after she left and found a note on her bed: “I’m not coming back for a long time. . . . I am safe where I am.”

Samantha spent her first few nights in Central Park, sleeping under a pine tree. She wore the cargo pants, steel-toed Brahma work boots, and blue hoodie that she had left home in. She kept an open book by her side so that anyone passing by would assume she was a student who had drifted off. Using her backpack as a pillow, she slept lightly, alert to the sound of footsteps. More than any noise, she feared the buzz of police radios. She avoided thoughts of danger by embellishing them, imagining that her absence was of central concern to the police. She survived her first days in New York, she said, by “acting like I was in some sort of spy novel.”

For hours every day, she wandered around the city, memorizing street names and bus routes, observing how the neighborhoods changed depending on the time of day. Her favorite time was just before dawn, when the bars let out. She watched drunken tourists shout foolish things as they searched for cabs, and enjoyed knowing that, comparatively, she had her bearings. Rarely sleeping more than four hours a night, she was constantly looking for opportunities to close her eyes. One of her first discoveries was the Museum of Natural History, where the bathroom stalls were conveniently narrow. She could sit on the toilet, her head against the stall, until she was woken at the end of the day by the sound of the janitor’s mop.

By sharing cigarettes, she befriended other homeless kids, many of whom hung out at the Apple Store on Fifth Avenue. Their poverty wasn’t apparent—most of them had stolen at least one trendy outfit—but Samantha could spot them easily, because of their backpacks and the way they lingered near the least impressive computers. (The pictures in their Facebook profiles had shiny new laptops in the background.) On rainy nights, Samantha occasionally slept with them on the A, C, E subway line, which has the city’s longest route. They called it “Uncle Ace’s house.” One person would stay awake, on guard against cops or thieves; the rest napped until the end of the line.

Many of the kids knew each other from the youth shelters, a decentralized and temporary system that turns away far more people than it houses. The city has roughly two hundred and fifty shelter beds for some four thousand youth between the ages of thirteen and twenty-five who are homeless on any given night. This substratum of the homeless population has historically been overlooked. Until 1974, running away was a crime. The federal youth shelter system wasn’t established until the seventies, following an era in which homeless kids were seen as middle-class dropouts who would shortly return home. The media portrayed them as rebellious flower children in search of a countercultural utopia. According to a 1967 article in the Times, the crisis involved “thousands of young runaways, particularly girls, who are flooding the Village area to live as hippies.”

During the recent recession, the rate of unemployment for people between the ages of fifteen and twenty-four reached nearly twenty per cent, a record high. Samantha dropped off her résumé (which she printed at libraries) at dozens of fast-food restaurants, but having no job experience, and given her appearance—she had packed no change of clothes—she seldom got called for interviews. She tried to make money by recycling bottles, but older homeless people had cornered the market. Instead, she shoplifted. It was easy, because of her wholesome looks. Half Cherokee on her mother’s side, she had sharp cheekbones, high-arched eyebrows, and long, shiny hair. She targeted chain stores like 7-Eleven and Whole Foods: she’d steal a package of oatmeal from one and then use the microwave at the other.