Zorro by Isabel Allende. Yes, Isabel Allende

Swashbuckling costume hero finds destiny in arms of literary novelist. Read Zorro's strangest adventure:

"One day in August 2003, a group of strangers knocked on the door of Isabel Allende's house in the exclusive enclave of Santa Rafael, overlooking San Francisco Bay. The imposing wooden door to La Casa de los Espiritus swung open to reveal a diminutive, sparkly-eyed, smooth-skinned woman of indeterminate age who bore only a passing resemblance to the photograph that has adorned Allende's books for the past 20 years.

'We own Zorro,' the strangers announced. 'Yeah?' she replied. 'So?'

The strangers were led by John Gertz. In 1920, Gertz's father had bought the rights to the Zorro character from the author of the original dime novel. Together with Disney, he had developed the multiple incarnations of the masked man - TV series, comic book, feature film - before Gertz Jr bought back the rights.

It had occurred to Gertz that Zorro had appeared in films, TV shows, comics - everything except serious literature. So the search began for a writer for hire, someone to fill in the backstory of Zorro, the early years; someone who, like Zorro, knew California well and could think in Spanish; someone with a track record in historical research; someone who could bring a Latin sensibility to the myth of the Mexican-American do-gooder. And so they knocked on Isabel Allende's door.

'I said, "What are you talking about? I'm a serious writer,"' the serious writer explains, sitting in her living room, a picture window providing a backdrop of clouds scudding across the bay. Rather than taking no for an answer, however, the visitors left a box full of Zorro artefacts - tapes of old movies, comics, recordings of the TV series. 'And so I fell in love again with Zorro,' she says, in her lilting English, 'because I had been in love with him when I was a child. He's the father of Batman and Superman. He's the father of all the action heroes with the double personality. Most of those guys have magic tricks. Zorro has only his own skills.' She prefers not to refer to the job as a commission. 'It was a proposition. They said, "We have the character and you have the talent to write the book. Are you interested?" I said, "OK, we'll go 50-50." And that was it.'

The decision to become a writer for hire was something Allende had previously resisted. Even the prospect of writing the story of her uncle, Salvador Allende, the former president of Chile who was assassinated in the 1973 coup, had not persuaded her. 'I could not be objective,' she says. 'I don't think I could write a novel about it, it would have to be biography and I am not good at that. I'm not the right person. I'm a lousy journalist because I can't stick to the plain truth, I have to embellish it.'

Pablo Neruda put it more plainly. 'You must be the worst journalist in the country,' the great poet told the young writer. 'You're incapable of being objective, you put yourself at the centre of everything. I suspect that you lie a lot, and when there is no news, you invent it. Wouldn't it be better to turn to writing novels? In literature, these defects are virtues.'

She took the poet's advice. In 1974, she fled her native Chile with her family. They arrived in Venezuela, where Allende's eyes, she says, were opened. 'Venezuela is a wild place. It's green, generous, there is something so different from Chile. It's a tropical country, so it has that energy we don't have in Chile. Chile is so restrained, restricted. I found a voice there that I wouldn't have had if I'd stayed in Chile.'

A letter written to her ailing grandfather became her first novel, The House of the Spirits. It established her as a significant voice in the exclusive male pantheon of Latin American fiction. She was, perhaps inevitably, tagged as a proponent of 'magical realism', and mention of her name would invariably be followed by that of Gabriel Garcia Marquez. Together with Of Love and Shadows and Portrait in Sepia, the novel eventually became a trilogy. Her other novels, including Eva Luna and Daughter of Fortune, have been notable for the same collision between personal and public histories that so marked out her debut. They are also notable for being bestsellers.

To Allende's delight, the job of writing Zorro suited her. 'This is totally out of the blue,' she says. 'I had so much fun writing this. There was no stress involved. My agent was horrified. Everybody was. Why would I do this? For the same reason I would wear the mask and the costume and take fencing classes.' Her account of Zorro's beginnings as a mestizo child in a California of missionaries and Indians is masterly, a page-turning, bodice-ripping tale of improbable duels, unlikely adventures and dastardly foes set against the grand currents of 18th-century European history and the emerging riches of the new world. The story, as she tells it, remains a fantastical romp. 'Sometimes people interview me about Zorro with this intensity, this seriousness, and I say, look, we're talking about Zorro, not Che Guevara. Calm down.'

The story of Zorro was hers to invent, and she applied the techniques she uses for her most intimate memoirs. There is even some magic, although mention of magical realism earns a rebuke. 'Magic realism is not like salt that you can sprinkle on everything,' she says, hinting at ice beneath the polite charm. 'I have written more than 15 books and there are elements of magic realism only in a few of them. But for some reason, Latin American writers who have used this end up being labelled with magic realism. But really, magic realism is just an acceptance that the world is a very mysterious place and we don't know all the answers.'

Like Zorro, Allende has led a nomadic life. And like him, she is an outsider. 'I have been a traveller, the daughter of diplomats, a political exile, an immigrant. So I don't think I have roots any more. I have them in books, in language, but not in a place. I think I am a good example of what California is all about. It's about immigration and diversity. And I'm very lucky because I'm legal in this country and I am my own boss, I don't have to be cleaning bathrooms. It's a nation within the nation. It's like slavery with a better name.'

Does she experience the discrimination directed against California's Latino underclass, derisively labelled as Mexicans regardless of origin? 'When I walk in the streets or buy something in Macy's, I'm a Mexican,' she says. 'Who would know that I'm from Chile? Of course, when I'm driving the freeway in a Lexus it's different. But when I get out of the car and am in the streets, I'm just another Latina woman.'

Allende is a writer steeped in superstition and method. She always starts a new book on January 8, the date she started The House of the Spirits. She works long hours alone in her office, an outhouse alongside the pool in her back garden. The main room in the office is dominated by her tidy desk, research meticulously laid out in neat piles. To one side is a prayer room, with cushions placed on the floor. Pride of place on her desk is taken by a photograph of her daughter, Paula, at the age of 27. Two years later, in 1992, she died of porphyria after a year in a coma. Her bereaved son-in-law, she tells me, eventually married a woman who shares her daughter's birth date.

When Paula and her brother Nicolas had grown up, Allende separated from their father. Within weeks she had met her current husband, a San Francisco lawyer named Willie Gordon.

Allende wrote a book about her daughter in part to record her life and in part to heal the pain of her loss, but the wounds remain. 'You never give up,' she says. 'I was clinging to her. But the truth is that the brain was dead. She had a tube and we had to feed her. The doctors said that they don't suffer, but how can you tell? There was a moment when the doctors said we should remove the tube, but I couldn't do it, because as a mother you nurture.'

Two other photographs occupy her desk, portraits of her grandparents, the subjects of The House of the Spirits. 'I really grew up in a house of the spirits,' she says, 'or really, the spirits that my grandmother thought that she was calling. Who knows if they came? It doesn't matter. Without the success of The House of the Spirits I probably wouldn't be a writer today. I'd be still working trying to make a living [she worked as a schoolteacher], support a family, which I did all my life. But the fact that the book was successful allowed me to write a second book, and then by the third book I could give up my day job and become a writer.'

The treadmill of the successful writer can leave her bemused, she says. 'Things overlap. Right now I am promoting Zorro but I am writing another book, supervising the translation for another book; and also the fact that my books are translated to more than 27 languages means that there is always an old book that is being published for the first time in places like Turkey. So I have journalists who come here to interview me for Eva Luna, which I wrote more than 20 years ago. And then I realised how much I had repeated myself. The characters may have different names, but they're all the same.'

She laughs at herself, an easy laugh. One imagines that she spends a lot of time laughing, even when the serious writer is at work. 'I think I live very much with the memory of some people that are now dead, or absent, so there's a lot of memories around my life.'

Then she returns to family. 'My granddaughter once said I have a big imagination. And I said, "What's a big imagination?", and she said, "You remember what never happened."' And then, again, the laugh. 'I think that defines my life.'"

ZORRO RIDES AGAIN. What next? Batman by Martin Amis? Spiderman by Ian McEwan? Superman by Philip Roth?