Caught out ... she made up her entire story. A moment later, a man with a red bandanna wrapped around his face appeared through the curtain of smoke that separated the living from the doomed. He patted down her burning clothes. "I've found a stairway," he said. She later identified him as Welles Remy Crowther, the 24-year-old equities trader who died after helping dozens of people to safety that day. The young hero guided her down 40 flights of stairs before handing her off to a firefighter, then went back to try to help others. She had just reached the street when the building collapsed. She woke up five days later as a "Jane Doe" in a New York hospital, one of the few who had been at, or above, the point of impact when the plane hit and survived. Dave hadn't been as lucky. He perished in the north tower. Tania's story was stunning. Word spread quickly through the close-knit survivor community that someone extraordinary had just come forward. The survivors embraced their newest member and she became a tireless advocate for them. Within months, Tania was leading tours of Ground Zero, telling her story to mesmerised visitors and powerful politicians alike. She forged a friendship with the parents of Welles Crowther, the man who saved her life, and promised to one day give them a piece of her burnt jacket because it was one of the last things their son ever touched. With Tania as a figurehead, the small support group grew into a fully-fledged advocacy organisation with considerable political might. Her name opened doors. She successfully lobbied curators of the World Trade Centre Memorial and Museum committee to ensure that the museum accurately reflected the journey of the survivors and commemorated their legacy in the story of 9/11. She led the fight to preserve the "survivors' stairway", which hundreds took to safety on the morning of the attacks. She befriended the World Trade Centre site manager and convinced him to give the survivors a private tour of Ground Zero, something they had asked for, but had never been granted. The others came to see Tania as the ?ber survivor. They were loyal to her, even when she was difficult and demanding. Even when it meant turning on one of their own - as happened in 2005, when she instigated a crusade to get rid of the group's founder, Gerry Bogacz, a survivor of both the 1993 and 2001 World Trade Centre attacks. Bogacz was forced out and Tania was elected president.

On the fourth anniversary of the attacks, Tania stood with then New York governor George Pataki, New York City Mayor Michael Bloomberg and former mayor Rudy Giuliani at the opening of the World Trade Centre tribute centre at Ground Zero, posing for pictures and bravely recounting her story. The New York Daily News devoted a column to her. "To behold Head's smile is to know the terrorists did not come even close to winning," they wrote. "To see that smile is also to be challenged to be as decent and positive as this true survivor." If only her story had been true. It was early in 2007, nearly four years into Tania's reign as America's most famous survivor, that Brendan Chellis, one of her closest friends from the World Trade Centre Survivors' Network, began to suspect her story. He spent hours on the internet one night trying to verify her account, but came up with more questions than answers. Tania had revealed her husband's last name to Brendan and a handful of other survivors. When he Googled Dave's full name, pages of biographical information popped up. Dave did die in the north tower. He had been featured in The New York Times' "Profiles of Grief." But there was no mention anywhere of a wife. As much as Brendan wanted to share his suspicions, he feared Tania would find out and turn the other survivors against him. He needed their support, so he kept quiet. Should we forgive the terrorists? No. I look at her as no more than a terrorist from September 11

Tania's behaviour became increasingly erratic that year. She was moody and unpredictable. She promised to donate her burnt jacket for display in the tribute centre, but repeatedly made excuses for not being able to provide it. Promised trips with survivor friends to her beach house in Amagansett, which she said was where Dave's belongings were kept, were always cancelled at the last minute. And no one ever got to meet anyone from Tania's life before 9/11. Not her family. Not Dave's parents. She couldn't even produce the golden retriever, Elvis, she said she bought with Dave. That summer, when The New York Times called asking to profile her for the sixth-anniversary commemoration, Tania's behaviour turned even more bizarre. She disappeared for weeks at a time without explanation. When she did show up to survivors' functions, she was often distracted and aloof. Her survivor friends were concerned that the stress of the impending anniversary was taking its toll. As Tania's anxiety mounted with each interview request from the Times, the survivors became increasingly agitated with the reporter for harassing her. Tania finally dispatched her friend Janice Cilento, a trauma therapist, to tell the Times to back off, but that didn't do any good, either. The reporter didn't understand why Tania couldn't answer a few basic questions. Janice suggested Tania get an attorney to ward off the Times, which she did. She asked Janice to come along. That's when the bottom fell out. Janice remembers the day in vivid detail. She was riding the lift up to the lawyer's office when Tania turned to her with a sheepish grin and confessed why she had been so rattled by the Times' request for an interview. "I can't do it because I'm not a citizen and I'm afraid they'll find out," she said. She was a citizen of Spain. Janice almost laughed. That's what all this had been about? "Oh my God, Tania," she said. "No one is going to care that you're not a citizen!" The relief she felt at finally having an explanation for Tania's resistance was short-lived, though.

While Tania conferred with the attorney, Janice read a magazine outside. After two hours, she was invited to join the meeting. Tania sat quietly as the lawyer spoke. No one would hold it against Tania that she didn't really work in the World Trade Centre, the lawyer said, trying to reassure her client. And no one would hold it against her that she wasn't married to Dave. Janice could hardly process what she was hearing. Janice missed her stop on the train ride home that night. She had been lost in thought, wondering how she would tell the others, and would they even believe her? When she finally got home, she called the reporter from the Times. "I hate doing this," she said, "but I think Tania has been lying." On September 27, 2007, the headline on the front page of The New York Times read, "In a 9/11 Survivor Tale, the Pieces Just Don't Fit." The story deconstructed Tania's 9/11 account, myth by myth. She didn't work for Merrill Lynch, as she had claimed. Nor did she graduate from American Ivy League schools. She didn't know the man named Dave, who wasn't married and whose family had never heard of her, nor was she saved by Welles Crowther, one of the great heroes of 9/11. She didn't own a beach house in Amagansett, and there was no burnt jacket to donate. Her name wasn't even Tania. It was Alicia. Alicia Esteve Head was born in July 1973 to a wealthy Spanish businessman and his much younger wife, the last of five children and the only girl. The family lived a prosperous life, moving between their sprawling Barcelona apartment, their villa in Majorca overlooking the Mediterranean and a country estate called El Campesino. Life revolved around yachting and horses and tennis at exclusive clubs. Alicia was "her parents' jewel", a family friend recalled. She was spoiled, granted every wish, no matter how extravagant. During summer holidays in Majorca, her parents flew in her three horses from Barcelona rather than listen to her whine about missing them. Her 16th birthday present was a diamond-encrusted Rolex watch worth tens of thousands of dollars.

But the one thing her parents couldn't give Alicia was what she most wanted: to be an American. "Americans were her idols and she was always talking about the US," says Sonia Humet, her closest girlhood friend. Alicia was already obsessed when Sonia met her in the early 1980s while both were attending a rich and conservative Opus Dei Catholic school in Barcelona. She was 10 years old and had an American flag hanging on her bedroom wall. "She very often talked about going to America," Sonia says. "It was a world that really appealed to her. She really made an effort to learn American English. In fact, she travelled there many times when we were young and she always talked about her trips." Alicia was a raconteur and Sonia loved hearing her tell stories, although she was never sure which were make-believe. Alicia had an eager imagination. When she was frustrated or bored, she spun yarns to accommodate the existence she wished for. Her tales, usually about imaginary boyfriends, were harmless enough, but they earned her a reputation as a storyteller. When Sonia accused her of telling tall tales, Alicia became angry and shut down. So Sonia eventually allowed her friend's imaginary lapses, and they remained the best of friends until Alicia left for Switzerland to attend private boarding school. In 1990, aged 18, Alicia returned to Barcelona from boarding school and was seriously hurt when travelling in a car with a group of friends along the Valencia coast. The driver lost control, the car crashed, and Alicia's right arm was severed and thrown from the vehicle. The story her family told, which is hard to imagine, was that when help arrived, she was found holding the arm. The arm was sewn back on, and in the following months, Alicia underwent multiple surgeries at the Mayo Clinic in the US, eventually regaining some use of the limb. She told different stories about her arm injury: when in Spain, she said that it happened when her wealthy boyfriend crashed his Ferrari at 200 kmh, sometimes claiming the boyfriend died in the accident; when in New York, after 9/11, she said that it was the result of injuries suffered in the 78th-floor sky lobby.

A year after the car crash, misfortune struck again when Alicia's father and eldest brother were accused of embezzlement in the highly publicized Planasdemunt financial scandal in Catalonia and sentenced to prison terms, spilling shame on the family name. Her parents' marriage fell apart and Alicia and her mother became estranged from her father and brothers. It was after those life-changing events, and especially after her family unit fractured, that Alicia split her world into two sides: reality and make-believe. "I saw it very clearly and other people who were close to her saw it as well," Sonia says. Sonia and Alicia remained friendly during those troubled times. "We talked about a lot of things," Sonia says. "But when I asked about the problems with her family one time, she said, 'No, no, no, no!' I never asked again." Alicia recovered enough to earn a degree from the European University in Barcelona. But the 25-year-old who surfaced in 1998 in the executive offices at Hovisa - a real-estate-development company - was a different person from the happy-go-lucky girl described by Sonia. Co-workers portray Alicia as a fiercely ambitious young woman who pitted people against each other and would do almost anything to get ahead. She flaunted her family's wealth and insisted on being at the centre of things, and she wasn't satisfied with being an executive assistant. She wanted to be in charge. When her boss returned to Japan in 2000, she left her job and enrolled in the prestigious Esade College in Barcelona. Her classmates remember her as ambitious and demanding, but generous. "Some of us had the sense that Alicia was trying to buy friendship," her classmate Brad Ervin recalls. "I had always found her slightly annoying with her attempts to control things." In 2002, Alicia graduated with her MBA. She told classmates that Barcelona wasn't big enough for her dreams and she was going to New York City. One year later, the woman with the prodigious imagination reinvented herself as Tania Head. Three months after that, she was on her way to becoming America's most famous survivor.

If her family knew anything about Alicia's forged life, they weren't saying. Linda Gormley, Tania's closest survivor friend, spoke with her mother, Acacia Head, on the night before the Times story ran and the mother claimed she knew nothing of her daughter's actions. Alicia's father and brothers didn't know where she or her mother were living until they saw them dodging TV cameras outside her apartment building in New York City via news reports broadcast in Spain. They had lost track of them after the contentious family split years earlier. As for the survivors, Linda summed up their feelings best. "We lost almost 3000 people on September 11 and what this woman did was terrorism to me," she says. "Should we forgive the terrorists? No. I look at her as no more than a terrorist from September 11. If I saw her again I would want to know 'Why?' Why would someone do something like this?" Pere Planas, a psychiatrist in Spain who didn't treat Alicia, but knew of her, says, "She wanted to be accepted and valued and New York gave her the opportunity to make the new 'I'. She had finished her stage here, she had reached certain goals, and she was dissatisfied in Barcelona. She assumed this situation, this pathology. She created a fantasy in New York that fit her like a glove." Many people in the US believe Alicia knew exactly what she was doing when she wrote herself into the 9/11 storyline and that she studied her subject well before presenting herself as a widow and a survivor. Sam Kedem, the trauma therapist who counselled her in New York, and was completely taken in by her, is in that group. "She was a professional," he says. "She knew every- thing there was to know about 9/11 because she studied it. "It's a case study," Kedem continues. "And it's not just a window into her personality and what she was capable of, but of what was going on with the whole 9/11 community and what they were feeling. The survivors needed and wanted a Tania so much that they helped create her."

Perhaps only Alicia Esteve Head knows why she did what she did, and she isn't talking. She continues to travel anonymously between Barcelona and New York. It was around the 10th anniversary of 9/11 that she was seen checking into a nearby hotel with her mother. So many questions remain, but this much is certain: the woman who became the face of one of the worst tragedies ever to mark American soil will forever be remembered as The Woman Who Wasn't There. The Woman Who Wasn't There by Robin Gaby Fisher and Angelo J. Guglielmo jnr (Allen & Unwin) is out next month. Like Good Weekend on Facebook to get regular updates on upcoming stories and events.