Describing the rescue, a Cleveland policeman is overwhelmed. "It's her," he remembers telling a dispatcher over his radio in May last year, weeping even as he recounts the story on camera. "Gina DeJesus and another girl."

The other girl was Michelle Knight, who was 21 when she was abducted by Ariel Castro 11 years earlier, in August 2002. Eight months after that, Castro kidnapped Amanda Berry, 16. A year later he took 14-year-old Gina DeJesus. The three young women were then imprisoned and raped by Castro for more than a decade in his house in suburban Cleveland.

Their rescue would have made global headlines under any circumstances, but the charismatic exuberance of one of their saviours ensured saturation coverage. Charles Ramsey was a two-time ex-con who had lived next door to Castro for the final year of the women's incarceration. When Berry stuck her arm out the front door one day in May 2013 and screamed for help, Ramsey responded with another neighbour, Angel Cordero. They kicked in the bottom section of the door, pulled Berry out and took her to a home across the road, where someone gave her a mobile phone to call the police.

Later, Ramsey described the moment to a TV reporter in the interview that would make him famous. "I heard screaming, I'm eating my McDonald's, I come outside, and I see this girl going nuts, trying to get out of the house. So I go on the porch. 'Help me get out,' she says. 'I've been here a long time.' I figured it was a domestic violence dispute.

So I open the door. And we can't get in that way 'cause of how the door is; it's so much that a body can't fit through, only your hand. So we kicked the bottom. And she comes out with a little girl and she says, 'Call 911. My name is Amanda Berry' ... Bro, I knew something was wrong when a little, pretty white girl ran into a black man's arms. Something is wrong here. Dead giveaway."

Ramsey's charming bluster and the public joy at the discovery of Castro's victims alive served as a distraction from the real horror of their ordeal. The forthcoming publication of Knight's autobiography, Finding Me, along with another, by Berry and DeJesus, yet to be published, will redress that.

I meet Knight in a New York hotel. She sits cross-legged in one of those oversized armchairs that boutique places favour in their lobbies these days. Though she is no longer the skeleton she was at the time of her rescue, the chair dwarfs her. In her book she describes how, as a teenager, people hesitated on meeting her, trying to work out whether or not she was a dwarf. She is 140 centimetres tall, or a little over four foot seven on the old scale.

Knight has short wavy hair, dyed a near-natural red, and wears thick glasses, which in the dim lobby light hide the colour of her eyes. I know her poor eyesight deteriorated further during her captivity because of the darkness; in any event, she rarely makes eye contact during our talk. She is weary after a long round of media interviews, polite without being friendly. Her publicist, Kathleen Schmidt, sits to one side tapping on her phone. She doesn't seem to be listening but notices silences immediately, stepping in to redirect the conversation.

It's an intrusion a journalist would normally bristle at, but I suspect I welcomed it as much as Knight. When you try to unpick a story like this, it is hard to distinguish the merely horrific from the truly unspeakable.

The abuse of Michelle Knight began long before she met Ariel Castro. Before the Cleveland Police and the FBI failed her, she had already been betrayed by her parents and relatives, her neighbours and teachers.

Some of Knight's earliest memories are of living in a brown station wagon with her two twin younger brothers, Eddie and Freddie. Sometimes her parents would park the car near an orchard on the outskirts of town, so they could pick their meals straight off the trees. When the family found housing, life got worse. The house soon filled with relatives and other hangers-on, so she didn't have her own place to sleep. She remembers hiding in a cupboard with the twins and a cousin called Mikey after gunfire broke out on the street.

It was during this period that a relative - whom Knight refuses to name - began to rape her, whispering into her ear that he would kill her if she told anyone.

At first he assaulted her once or twice a week, but as she grew older the attacks came each night. "When I turned 11, I got my period," she says in Finding Me, written with Michelle Burford. "I didn't know it was my period because I had been bleeding down there since I was five. And by the time I was 11, the bad things that were done to me started getting worse. A lot worse."

Though no one in the family worked, Knight was responsible for the care of her brothers and any cousins who may have been staying. She remembers a constant struggle to find enough food. Most of her teachers chose not to notice the girl with threadbare clothes who attended school sporadically and was always hungry, and her classmates hated her. "Nobody was my friend. And I mean nobody," she writes. At 15, Michelle weighed just 35 kilograms and had no chance of fighting off her abuser. One night, as he watched porn, she spiked his bourbon with sleeping pills, slid out of his bed and ran.

What followed was the happiest period of her childhood. She lived with a drug dealer called Sniper, who used her as a runner. Sniper had found Knight living under a bridge in a wheelie bin and took her back to his house. "I figured it couldn't be anything worse than what I had gone through during the first 15 years of my life," she writes.

"Everybody has their own outlook on a drug dealer," Knight tells me. "But I say that he had a gentle heart and he had a big heart. He never hurt me and he never once made me feel that I had to run or be uncomfortable."

After about six months Sniper was arrested, and Knight ended up back under the bridge until her father picked her up and dragged her home. The abuse by the unnamed relative resumed. " 'You thought you could get away from me, you little pussy,' the man whispered into my ear that evening," she writes. "He swirled his slimy tongue around in my ear." Knight writes that shortly after this she fell pregnant to a high-school boyfriend. "I ... loved that I got to be with him because I wanted to - and not because I was forced." The relationship did not last but the birth of her son, Joey, thrilled her and became the focus of her life.

Joey was born in 1999 and Knight, then aged 18, left school to care for him. In 2002 she started looking in earnest for a job, walking the streets of Cleveland to leave applications at fast-food restaurants. She never had any luck, in no small part because she was too short to reach high shelves or cash registers. While she was job hunting, Joey was left at home with Knight's mother, Barbara. By then Knight's father had left and a boyfriend called Carlos had moved in.

One day in June that year, Carlos, drunk, lunged at Knight, but was distracted by Joey's screams. He then angrily grabbed the boy, twisting his leg so badly it broke, resulting in Joey being removed by social services.

The passages describing her son being forcibly taken are among the most difficult to read in the book, despite the savagery of the abuse Knight would go on to suffer.

To regain custody, Knight had to demonstrate she could safely look after a child, so she moved in with a cousin, kept up her job search and attended regular meetings with social services. Without money for transport, Knight walked to the meetings, which were held all across the city as Joey was being moved from foster home to foster home.

One day, after she became lost, Knight asked a woman at the checkout of a dollar store for directions. The conversation was overheard by Ariel Castro, the father of one of her friends. "I know exactly where that is," said Castro and offered to drive her. It was August 23, 2002. Saying he had to pick something up, he instead took her to his house on Seymour Avenue in suburban Cleveland, just a few blocks from Knight's home. Once there, he coaxed her inside by telling her his dog had a litter of puppies. She could have one for Joey.

Knight knew something was not right, but she was worried about appearing to be rude, so she waved to a man in the neighbouring garden and walked inside. Castro had planned for this moment. He cornered her in a squalid upstairs bedroom, tied her hands and feet, then strung her up on a wire he had tethered between two poles on either side of the room, beating her when she screamed. He put a dirty sock in her mouth, covered it with duct tape and sexually assaulted her.

Days later, Castro moved Knight to his basement. "What happened over the next three hours is still hard for me to think about," she writes. "He didn't just rape me the way he had upstairs. He murdered my heart - or at least the small part that was still left after what I went through when I was a girl." She was raped constantly and fed rarely. Castro chained her to a pole and forced a motorcycle helmet over her head.

In the basement, Knight lost track of time and sometimes found herself talking aloud to Joey. She soon learnt the rhythms of Castro's life by interpreting the noises in the house - his phone alarm going off in the morning would sometimes be followed by silence as he went off to buy her an Egg McMuffin for breakfast. "If you wanna eat today, you better do what I tell you," he would say on his return. Then he would leave for the day dressed in his school bus driver's uniform. On the weekends, his salsa band would sometimes rehearse upstairs. Castro, who always wore a gun on his hip, told her he would shoot her if she made a sound.

It was around this time that Castro began telling Knight that nobody was looking for her. No flyers were posted around the neighbourhood; there had been no tearful appeals on TV, no police doorknocks. "I can do whatever I want to you, nobody gives a crap," he would say, smirking. She believed him, too. After all, people had seen her talking to Castro in the dollar store. She had waved to the neighbour as she went into the house. She should have been easy to find.

After some weeks, Knight was taken upstairs to the second floor, where she was chained naked to a bed. The windows were boarded up and the door padlocked. Around eight months into her imprisonment, Castro led Knight downstairs for her first shower. She wept when she saw her bruised and emaciated figure in the mirror of a filthy bathroom. She took some scissors and cut off her encrusted hair.

The following April, Knight saw a news report on a TV Castro had given her about a 16-year-old blonde girl called Amanda Berry, who had disappeared from a nearby Burger King. Knight knew Berry from school, and she suspected Castro immediately. He had long talked about how much he wanted to have sex with a blonde like Christina Aguilera or Britney Spears. Soon loud music was blaring constantly from the basement.

After about three weeks, he brought Berry into Knight's bedroom, introducing her as his brother's girlfriend. Knight remembers how Berry gazed at her quietly, and at the filth around the bed, the mounds of takeaway food containers, the bucket she used as a toilet, the boarded-up window. Berry was then chained in another room. As Knight remembers it, after Berry's arrival Castro began assaulting her more often. He raped her in the morning before work and two or three times in the evening. " 'She don't want to do it,' he told me, 'so you are going to have to do it,' " she writes.

Watching the news, Knight could not help but notice how much effort was going into the search for Berry. "Even though I had been missing for a while, you'd think that Amanda's disappearance would trigger questions about whether the same person had kidnapped me - that is, if anyone had made a big deal about me being gone in the first place."

It was around this time that Knight realised she was pregnant. "I missed my son so much my body ached ... at least I could have something that was all mine, a baby growing inside of me, even though the baby's father was the devil himself." Castro discovered the pregnancy a few weeks later when breast milk leaked from Knight's nipples during a rape. He began to starve her to force a miscarriage, and when that did not work he beat her until she lost the baby. Knight was to fall pregnant four more times, provoking the same response from Castro. She was beaten so savagely on the last occasion that she can no longer have children.

When Gina DeJesus was abducted in april 2004, the terrible routine was repeated in Castro's home. After her time in the basement, Castro led her into Knight's room. For the first time in years, the chain around Knight's neck was removed. DeJesus had been a good friend of one of Castro's daughters, Rosie.

At first Castro separated the two before he assaulted them, but soon he began to rape one or the other as they were chained together. Still, Knight believed she was subjected to the worst of Castro's torture. "It's not that he was nice to either of them - far from it," she writes. "But I felt as if I was the prisoner who got beat down the most. And my perception was that on some days I was the only one he had raped."

In 2006, Berry had a baby daughter. Knight delivered her in a wading pool, with Castro threatening to kill her if the child died. Berry named the girl Jocelyn and Castro's fantasy family altered to accommodate the baby's presence. He insisted the women had to use different names around Jocelyn so that she did not repeat their real names outside the house. He planned to give Jocelyn some freedom. Knight went by "Juju" and DeJesus became "Chelsea". "She brought so much life and joy into that house," says Knight during our chat. "It made me think of my son and how he was growing just like her."

Jocelyn was rarely allowed outside but was free to move around the house. Castro began unchaining the women more and occasionally letting them downstairs. Even during these moments Knight was made to fill excluded from Castro's "family". While the others were allowed to sit on the couch with him to watch TV, or at the table for a meal, Knight had to stand in the corner.

When Jocelyn was five, Castro took her to a fair and she returned with a hot dog each for Knight, DeJesus and Berry. Knight told Castro she was allergic to mustard, but he beat her until she ate it. Her anaphylactic reaction and the long illness it prompted was the closest she came to death. DeJesus nursed her back to health.

By this time, conditions inside the house were falling apart. Castro had lost his job and was constantly home. Knight remembers him complaining that he could no longer afford to keep the women. She believes this may be why he allowed his security to lapse. One morning, Jocelyn ran up and down the stairs yelling out, "Daddy, Daddy". Knight heard Berry's bedroom door opening, but without the usual jiggle of padlocks. Later again, Knight heard pounding on the front door and thought drug dealers were trying to break in. She hid behind a TV cabinet. When she finally saw two uniformed officers, she threw her arms around a policewoman's neck and refused to let go. Castro was apprehended later that day in the car park of a nearby McDonald's.

After a night in hospital, Berry and DeJesus were released to their families. Knight was in a far worse state and stayed longer. Her brothers visited, though Freddie told CNN he had been kicked out of home at 14 and had not known Knight was missing.

Since leaving hospital, Knight has had nothing to do with her family, although her mother, Barbara, has said she wants to see her. Barbara disputes Knight's account of her childhood. She speaks of a happy girl who once fed apples to a neighbour's pony. Knight also has not been reunited with Joey, now aged 14, though sometime after her escape his adoptive family sent her eight photographs showing a very happy boy. More recently, she has exchanged letters and cards with him.

"It helps a little but it does not help the physical thing; you know, where you want him in your arms and to tell him that you love him," she tells me. She hopes to meet Joey when he is older, but is glad that at least he knows her name and that she loves him.

Knight was the only one of Castro's three captives to face him in court in August last year. "You deserve to spend your life in prison. I can forgive you, but I will never forget," she told him. A month later, Castro was found dead in his cell; he had hung himself. "I was sad because I feel he shouldn't have had to feel like he had to kill himself, but I understand why he did it," says Knight. "He could not accept the fact he did what he did and he could not suffer the consequences of what was going to happen to him in prison."

She thinks she knows why he was driven to abduct and abuse the three women. "He just wanted, like everybody else, a family that loved him, that did not run, that stuck around." Knight tells me it has been harder to forgive her family than it was to forgive Castro; she feels as though they hurt her more than he ever did. In her book, she says nothing about the Cleveland Police Department's failure to search for her, nor the FBI's decision to remove her from its missing list after just 15 months.

Knight and DeJesus no longer speak. "We kept in touch for a little while, then she decided she needed time to heal and I said, 'Okay you do what you need to do, you take care of you, I'll take care of me and eventually one day we will be back together.' " When I ask if she is hurt that DeJesus and Berry are now writing a book together, she falls silent and her publicist, Schmidt, interrupts. "We are not broaching that," she says.

Today, Knight lives in her own apartment in Cleveland with green walls and big windows. She says it is a thrill to get up and leave the house each day. She is working towards finishing her high-school diploma and is studying cooking. Her classmates, she explains, understand why she does not want to talk about her past.