A body is found in the frozen North Dakota woods. The cops say the dead Japanese woman was looking for the $1m she saw buried in the film Fargo. But the story didn't end there. By Paul Berczeller

It was just one of those crazy little stories buried in the morning paper. "News of the Weird," as it's sometimes known, true stories about real life events so unlikely and ridiculous that they attain a kind of absurd magnificence in the retelling. "Cult film sparked hunt for a fortune," was the small headline that attracted my attention that morning back in December 2001. "A Japanese woman searched a remote area of America during a quest to find a briefcase containing almost $1m buried by a fictional character in the cult film Fargo."

According to the article, a 28-year-old woman had left Tokyo a month earlier to travel to North Dakota, in America's midwest. The police were called after she was spotted wandering around the outskirts of the state capital, Bismarck. When officers interviewed the woman, she showed them a "crude map" that was supposed to show the location where the money was hidden in the movie. A perplexed spokesman for the Bismarck police was quoted saying: "We tried to explain to her that it was a fictional movie, and there really wasn't any treasure."

But whatever the police said apparently didn't deter Takako Konishi from her strange quest, which ended with her pointless death. "A hunter later found her body in woodland," the story concluded, "near the village of Detroit Lakes, which lies on a road between Fargo and Brainerd."

As any fan of the Coen brothers' 1996 comic film noir knows, most of Fargo is actually set in and around a gentle American small town called Brainerd, Minnesota, proud home of the mythical mighty lumberjack Paul Bunyan. The movie tells the story of an uber-loser Minneapolis car salesman, Jerry Lundegaard (William H Macy), who comes up with a knuckleheaded plan to have his own wife pretend-kidnapped by hired thugs in order to swindle his wealthy father-in-law out of the ransom. Needless to say, the whole thing goes horribly wrong, one thing leads to another and before you know it bodies are dropping all over the place. Enter Brainerd police chief Marge Gunderson (Frances McDormand, who won a best actress Oscar), hot on the trail of the two spectacularly incompetent yet murderous kidnappers, Carl Showalter (Steve Buscemi) and his heroically sullen Swedish partner in crime Gaear Grimsrud (Peter Stormare).

Perhaps the most memorable scene in a memorable movie finds Buscemi's character in a car parked by the side of a deserted road outside Brainerd. With one hand he's pressing a piece of dirty cloth up to his jaw - oozing with blood from a bullet through the face - with the other he opens a briefcase overflowing with $100 bills. This is the ransom money, but it's much more than he expected - about a million dollars more. "Jeshush Shrist," he exclaims. "Jeshush fuchem Shrist!" It's his lucky day and he decides to celebrate by double-crossing his colleague. Buscemi gets out of the car, briefcase in hand, and doggedly slogs through a snowy vastness towards a barbed-wire fence, the only thing in sight. It's the middle of nowhere. He kneels down at one of the fence posts and frantically digs away at the snow with an ice-scraper from his car. When that's done, he throws the suitcase into the hole and covers it up. The would-be criminal mastermind stands, satisfied for a moment until he happens to glance around him. A line of identical fence posts stretch in either direction as far as the eye can see. He ponders the situation for a moment, then has a brainstorm: he sticks the small red ice-scraper in the snow to mark the spot.

It's yet another absolutely positively foolproof plan in the movie that's just not going to work out. Soon enough the sullen Swede is captured by Chief Margie while in the act of feeding his mastermind accomplice into a mechanical woodchipper. The suitcase full of ransom money - the desperate pursuit of which started everything off - is lost somewhere out in the snowy vastness. And other than Carl Showalter - last seen with his leg sticking out of a woodchipper - no one knows where it is, or even that it still exists.

Unless you count those of us in the audience. And while we are allowed - encouraged - to believe that a fiction film is real while we're watching it, the moment the lights go up it's a different story. Fargo, the dream, is over. Sometimes it's not easy. But there's no choice; we know it's time to go home. But it seemed that for some unknown reason, by the time she was first spotted in Bismarck in November 2001, a 28-year-old Japanese girl named Takako Konishi no longer could.

It was late February and I was in Bismarck on the trail of Takako Konishi's last days. The Coens memorably describe this part of America - they grew up nearby - as "Siberia with family restaurants". The story had stayed with me ever since I first read about her. What was it that made me want to know more? Like her, I loved the movies, and especially Fargo. And because I did I couldn't quite laugh at her apparent desire - however irrational - to burst through the screen and make Fargo real. It's a common fantasy among movie lovers. The difference is, she did it.

Even the essential postmodern twist, the confusion between fiction and reality fundamental to Takako's story, turns out to have been anticipated by Joel and Ethan Coen in their film. Fargo opens with a title card proclaiming: "This is a true story. The events depicted in this film took place in Minnesota in 1987." Earnest journalists who went in search of the "real" woodchipper murders were outraged when, after months of wild goose chases and increasingly deadpan obfuscation by the film-makers, they finally admitted that the title card was actually an elaborate hoax - their way of "poking a hole in the true story balloon", according to William H Macy.

So Fargo was not, in fact, based on a true story. None of it really happened. There is no real "Jerry Lundegaard" out there. Yet from what I read on the internet, the police apparently believed that the ironic and essentially cautionary title card was at least partially responsible for Takako's delusion and subsequent death.

There's yet another meta-twist: I went to North Dakota to make a film about Takako's "true story" for Channel 4. My idea was to reconstruct the last week of Takako's life using still photographs, mixed with some digital video, in a kind of contemporary response to Chris Marker's legendary 1964 film roman short, La Jetée. I was going to interview the people she encountered along the way, hoping to excavate the real story and the real person beneath the urban myth. The interesting thing - or what I hoped would be interesting - was that the eyewitnesses would then recreate those encounters on film, "playing" themselves across from an actress playing Takako.

The inhabitants of Bismarck are certainly among the nicest people in the world, but that doesn't stop many of them from engaging with strangers as one would with an extraterrestrial - politely, but plainly astonished at its existence. My cameraman Mark and I were strange enough. But when Mimi walked into a busy truck-stop for breakfast, every single baseball-capped head in the place swivelled instantly in her direction. Perhaps that had something to do with the short black miniskirt and high black boots I had her wearing in the dead of winter. Mimi, my star, was a Japanese music promoter living in London. By the time we arrived in Bismarck, she had transformed herself unrecognisably into Takako. The miniskirt and boot outfit - topped off with a black leather backpack - was classic fashion-crazy Tokyo girl, circa 2001. That's how Takako had dressed for her quest in America - one of the few things I actually knew about her for sure.

"Girls in North Dakota kinda don't dress like that," Officer Jesse Hellman told me. Adding politely: "Probably 'cause of the weather." Jesse was the police officer in the original article that had sent me on my own quest. He was the source for what we knew about Takako's hand-drawn treasure map, the first person who tried to figure out what she was doing there alone in North Dakota.

That was a lot harder than it sounded, he said. She didn't speak English and he didn't speak Japanese. He looked for help - even calling all the Chinese restaurants in town, figuring that might be close enough - but there seemed to be no one in the entire capital city of Bismarck who was Japanese. So they communicated with each other the best they could, one word at a time with a little pocket translator she had brought with her from home. "That didn't help at all. Confused me even more," he recalled, shaking his head gravely.

We all loved Jesse. He was especially nice to Mimi, whom he treated with a gentle solicitude both on and off camera, exactly how he must have been with Takako. He spoke to Takako for four hours after she had been dropped off at the police station by a concerned citizen, a trucker, who had seen her wandering around. Jesse did his best to help her, but he felt guilty now. "I didn't think I had helped her at all, but I didn't know what else I could do. I felt really bad for her," he said, stealing a sad glance at Mimi.

Jesse told me about Takako's map, a white piece of paper, on which she had drawn a road and a tree. "That's where she wanted to go, she kept pointing at it. She kept saying something over and over, like 'Fargo' or some word like that. Like that's where she wanted to go. I remember that real clearly. But in North Dakota, practically everywhere you look, there's a road and a tree. So that didn't really help much."

"I had never seen the film Fargo, but another officer in the station had seen it and he told me that there was money buried in this movie. And then we started to think that she had this false impression that the money buried by a road by a tree was real in the movie. That's where she wanted to go. We thought that was really odd, but suddenly it all began to make sense."

Jesse remembered how he and the other officer tried to explain to Takako that Fargo was just a movie, that it was all make-believe. There was no treasure buried anywhere really, they kept trying to make her understand. Takako was polite as ever, very friendly and co-operative, but Jesse could tell she wasn't listening. They finally had to give up. "I remember it real clear. Guess her mind was made up. She was just dead set on going to Fargo," Jesse said. He took her to the bus station to catch the next Greyhound east. The next time he thought about her was when the detectives called from Detroit Lakes, over the state line in Minnesota, to say that a Japanese girl had been found dead in their woods, with his card in her wallet.

It took about four hours to drive from Bismarck to Fargo, down Interstate 10, a long, flat, almost mesmerisingly straight road. For hundreds of miles on end nothing changed in the blank, white landscape except the remaining distance to Fargo on the signs by the side of the road.

We drove into town at golden hour, just in time to shoot Mimi-as-Takako arriving at the mysterious destination of her quest. A frozen wind blew against her face as she walked down a lonely road, a giant blue water tower lit up in the distance, the word "Fargo" illuminated in the night.

We checked into the Quality Inn, the most depressing, yellow-fluorescent-lit kind of downtown budget motel, a few blocks from the Greyhound terminal. It was neighboured by an army induction station that ensured a steady supply of drunk 18-year-old recruits carousing through the dark halls. Closing the door of my room behind me, I experienced an almost paralysing sense of hopelessness, something so strong and unexpected that I had to sit down. Part of it was the hotel itself. But it was also that I was in the room where Takako had spent the last two nights of her life. I don't know when I had come up with that bright idea, but I changed rooms right away.

By the next evening, Mimi, especially, seemed depressed. Takako was weighing heavy on her; she was tired of being watched in her miniskirt, tired of the recruits' wolf whistles, tired of looking like Takako, tired of being Takako, that sad girl without hope. I think she was also dreading the final death scene we would shoot in two days time.

There was the last night-clerk scene to shoot before we could go to sleep. He was everything that I had hoped the night clerk of a creepy Fargo budget motel would be. Bug eyes, sallow skin, sweaty palms and a wonderful Vincent Price-style laugh. He was originally from Chiswick. I never did find out how he had ended up here.

He had spoken to Takako a few times. She seemed lonely. "But then again, people aren't generally at their happiest when I see them on my shift," he said. "It's funny," he went on, "I was surprised when I heard how she died looking for the ransom in the movie. She never mentioned anything to me about Fargo or any other kind of movie."

I asked him what they did talk about. It turns out that in the last days of her life, Takako didn't talk to anyone in Fargo about Fargo, the movie. She was thinking of something else. "She started asking about seeing the stars," said the night clerk. "Which I thought was a little strange, because it was November and it isn't that warm outside in the middle of the night, but I wanted to help so I showed her this place on the map where it would be nice to watch the stars. She seemed to be happy after that."

Takako left for Detroit Lakes, the final stop on her odyssey, the next morning. And we left for there as well.

We were shooting the final death scene. I was standing in a forklift with Mark looking down over Mimi sprawled with her face in the snow. Mimi had been dreading it. Now she didn't want to let Takako go. She was so cold that between takes I had to carry her to the warm car. But she never complained. The actual place where Takako had died was a little walk through the birch woods, but I didn't want to shoot there. Mimi, a Buddhist, brought some oranges as a present for the spirit of her fellow Japanese girl and laid them against the tree which Takako was leaning against when she died.

It was only late in the investigation that they found out about the suicide note, Chief Keena had told me the day before. He was a huge Nordic guy in his mid-40s. When the press first tied Takako's death to the movie, the phone in his office went crazy. He wasted weeks giving interviews to journalists from all over the place, he said. Must have been a slow news day, he mused.

The chief said that they had a lot of theories at first about what might have happened - homicide, a drug overdose, hypothermia - but nothing that solved it for sure. That's why he was happy when he heard about the suicide note Takako had mailed to her parents the same day that she encountered Jesse in Bismarck. They only received it three weeks after her death.

"You know, the whole Fargo thing grew to mythical measures, but for us here at the DLPD, the investigation was pretty straightforward and we had a job to do in spite of what anyone else wanted the story to be."

Something I imagine Marge Gunderson might have said if she had been interviewed by journalists after the "woodchipper" murders. If Fargo wasn't only a movie and she wasn't a fictional character. But Takako hadn't been fictional. She wasn't simply a character whose death (and therefore life) was an absurd story, the butt of some global joke at her expense. She was more than a tiny vanishing twinkle of entertainment.

It turned out that the story I had come to find in the upper midwest never existed. Yes, she had come to the upper midwest to kill herself. But not because of Fargo. It seemed the whole treasure story was nothing more than a Coen brothers-style series of tragic misunderstandings. Nothing more than the figment of an earnest policeman's imagination. Nothing more than a tale that people wanted to believe.

Mimi left for home after a last prayer by Takako's tree. Mark and I went on to Japan to find someone who knew Takako before she left on her last journey. We got luckier than we ever imagined, winning full cooperation from Takako's landlady. I found out that Takako had once been a normal happy office girl in Tokyo. And that one day everything changed and she fell apart, started drinking heavily, maybe even got a job in the sex industry. The landlady thought that she had been left brokenhearted by a man. She even cried for me on camera. It had all gone well.

When I got back to London I found out more about Doug, the American married businessman in Tokyo who Takako couldn't get over. I found out that she had been to Minnesota three times before - possibly with Doug. I found out that the last call she ever made was to him. She made it from her hotel room in Bismarck, the day before she left on the bus for Fargo. Takako probably died of a broken heart. That's the true story.

I'm telling you all this because I know you want to know. Everyone loves a true story, the stranger the better. But I don't think all that matters to me any more. Somehow, the story ended for me that day I was looking down from the forklift at Mimi face down in the snow. I felt sorry for Takako.