The street called Solvandan consisted of single-family homes and was about five minutes from the hotel. There was no answer when Blomkvist rang the bell. It was 9:30, and he assumed that Burman had left for work or, if he was retired, was out on an errand.

His next stop was the hardware store on Storgatan. He reasoned that anyone living in Norsjo would sooner or later pay a visit to the hardware store. There were two sales clerks in the shop. Blomkvist chose the older one, maybe fifty or so.

"Hi. I'm looking for a couple who probably lived in Norsjo in the sixties. The man might have worked for the Norsjo Carpentry Shop. I don't know their name, but I have two pictures that were taken in 1966."

The clerk studied the photographs for a long time but finally shook his head, saying he could not recognise either the man or the woman.

At lunchtime he had a burger at a hot-dog stand near the bus station. He had given up on the shops and had made his way through the municipal office, the library, and the pharmacy. The police station was empty, and he had started approaching older people at random. Early in the afternoon he asked two young women: they did not recognise the couple in the photographs, but they did have a good idea.

"If the pictures were taken in 1966, the people would have to be in their sixties today. Why don't you go over to the retirement home on Solbacka and ask there?"

Blomkvist introduced himself to a woman at the front desk of the retirement home, explaining what he wanted to know. She glared at him suspiciously but finally allowed herself to be persuaded. She led him to the day room, where he spent half an hour showing the pictures to a group of elderly people. They were very helpful, but none of them could identify the couple.

At 5:00 he went back to Solvandan and knocked on Burman's door. This time he had better luck. The Burmans, both the man and the wife, were retired, and they had been out all day. They invited Blomkvist into their kitchen, where his wife promptly made coffee while Mikael explained his errand. As with all his other attempts that day, he again drew a blank. Burman scratched his head, lit a pipe, and then concluded after a moment that he did not recognise the couple in the photographs. The Burmans spoke in a distinct Norsjo dialect to each other, and Blomkvist occasionally had difficulty understanding what they were saying. The wife meant "curly hair" when she remarked that the woman in the picture had knovelhara.

"But you're quite right that it's a sticker from the carpentry shop," her husband said. "That was clever of you to recognise it. But the problem was that we handed out those stickers left and right. To contractors, people who bought or delivered timber, joiners, machinists, all sorts."

"It's turning out to be harder to find this couple than I thought."

"Why do you want to find them?"

Blomkvist had decided to tell the truth if anyone asked him. Any attempt to make up a story about the couple in the pictures would just sound false and create confusion.

"It's a long story. I'm investigating a crime that occurred in Hedestad in 1966, and I think there's a possibility, although a very small one, that the people in the photographs might have seen what happened. They're not in any way under suspicion, and I don't think they're even aware that they might have information that could solve the crime."

"A crime? What kind of crime?"

"I'm sorry, but I can't tell you any more than that. I know it sounds bizarre that someone would come here almost forty years later, trying to find this couple, but the crime is still unsolved, and it's only lately that new facts have come to light."

"I see. Yes, this is certainly an unusual assignment that you're on."

"How many people worked at the carpentry shop?"

"The normal work force was forty or so. I worked there from the age of seventeen in the mid-fifties until the shop closed. Then I became a contractor." Burman thought for a moment. "This much I can tell you. The guy in your pictures never worked there. He might have been a contractor, but I think I'd recognise him if he was. But there is one other possibility. Maybe his father or some other relative worked at the shop and that's not his car."

Mikael nodded. "I realise there are lots of possibilities. Can you suggest anyone I could talk to?"

"Yes," said Burman, nodding. "Come by tomorrow morning and we'll go and have a talk with some of the old guys."

Salander was facing a methodology problem of some significance. She was an expert at digging up information on just about anybody, but her starting point had always been a name and a social security number for a living person. If the individual was listed in a computer file, which everyone inevitably was, then the subject quickly landed in her spider's web. If the individual owned a computer with an Internet connection, an email address, and maybe even a personal website, which nearly everyone did who came under her special type of research, she could sooner or later find out their innermost secrets.

The work she had agreed to do for Blomkvist was altogether different. This assignment, in simple terms, was to identify four social security numbers based on extremely vague data. In addition, these individuals most likely died several decades ago. So probably they would not be on any computer files.

Blomkvist's theory, based on the Rebecka Jacobsson case, was that these individuals had fallen victim to a murderer. This meant that they should be found in various unsolved police investigations. There was no clue as to when or where these murders had taken place, except that it had to be before 1966. In terms of research, she was facing a whole new situation.

So, how do I go about this?

She pulled up the Google search engine, and typed in the keywords [Magda] + [murder]. That was the simplest form of research she could do. To her surprise, she made an instant breakthrough in the investigation. Her first hit was the programme listings for TV Varmland in Karlstad, advertising a segment in the series "Varmland Murders" that was broadcast in 1999. After that she found a brief mention in a TV listing in Varmlands Folkblad.

In the series "Varmland Murders" the focus now turns to Magda Lovisa Sjoberg in Ranmotrask, a gruesome murder mystery that occupied the Karlstad police several decades ago. In April 1960, the 46-year-old farmer's wife was found murdered in the family's barn. The reporter Claes Gunnars describes the last hours of her life and the fruitless search for the killer. The murder caused a great stir at the time, and many theories have been presented about who the guilty party was. A young relative will appear on the show to talk about how his life was destroyed when he was accused of the murder. 8:00 p.m.

She found more substantial information in the article "The Lovisa Case Shook the Whole Countryside," which was published in the magazine Varmlandskultur. All of the magazine's texts had been loaded on to the Net. Written with obvious glee and in a chatty and titillating tone, the article described how Lovisa Sjoberg's husband, the lumberjack Holger Sjoberg, had found his wife dead when he came home from work around 5:00. She had been subjected to gross sexual assault, stabbed, and finally murdered with the prongs of a pitchfork. The murder occurred in the family barn, but what aroused the most attention was the fact that the perpetrator, after committing the murder, had tied her up in a kneeling position inside a horse stall.

It was later discovered that one of the animals on the farm, a cow, had suffered a stab wound on the side of its neck.

Initially the husband was suspected of the murder, but he had been in the company of his work colleagues from 6:00 in the morning at a clearing twenty-five miles from his home. It could be verified that Lovisa Sjoberg had been alive as late as 10:00 in the morning, when she had a visit from a woman friend. No-one had seen or heard anything; the farm was five hundred yards from its nearest neighbour.

After dropping the husband as a suspect, the police investigation focused on the victim's twenty-three-year-old nephew. He had repeatedly fallen foul of the law, was extremely short of cash, and many times had borrowed small sums from his aunt. The nephew's alibi was significantly weaker, and he was taken into custody for a while, but released for lack of evidence. Even so, many people in the village thought it highly probable that he was guilty.

The police followed another lead. A part of the investigation concerned the search for a pedlar who was seen in the area; there was also a rumour that a group of "thieving gypsies" had carried out a series of raids. Why they should have committed a savage, sexually related murder without stealing anything was never explained.

For a time suspicion was directed at a neighbour in the village, a bachelor who in his youth was suspected of an allegedly homosexual crime - this was back when homosexuality was still a punishable offence - and according to several statements, he had a reputation for being "odd." Why someone who was supposedly homosexual would commit a sex crime against a woman was not explained either. None of these leads, or any others, led to a charge.

Salander thought there was a clear link to the list in Harriet Vanger's date book. Leviticus 20:16 said: "If a woman approaches any beast and lies with it, you shall kill the woman and the beast; they shall be put to death, their blood is upon them." It couldn't be a coincidence that a farmer's wife by the name of Magda had been found murdered in a barn, with her body so arranged and tied up in a horse stall.

The question was why had Harriet Vanger written down the name Magda instead of Lovisa, which was apparently the name the victim went under. If her full name had not been printed in the TV listing, Salander would have missed it.

And, of course, the more important question was: was there a link between Rebecka's murder in 1949, the murder of Magda Lovisa in 1960, and Harriet Vanger's disappearance in 1966?

On Saturday morning Burman took Blomkvist on an extensive tour of Norsjo. In the morning they called on five former employees who lived within walking distance of Burman's house. Everyone offered them coffee. All of them studied the photographs and shook their heads.

After a simple lunch at the Burman home, they got in the car for a drive. They visited four villages near Norsjo, where former employees of the carpentry shop lived. At each stop Burman was greeted with warmth, but no-one was able to help them. Blomkvist was beginning to despair.

At 4:00 in the afternoon, Burman parked his car outside a typical red Vasterbotten farm near Norsjovallen, just north of Norsjo, and introduced Mikael to Henning Forsman, a retired master carpenter.

"Yes, that's Assar Brannlund's lad," Forsman said as soon as Blomkvist showed him the photographs. Bingo.

"Oh, so that's Assar's boy," Burman said. "Assar was a buyer."

"How can I find him?"

"The lad? Well, you'll have to dig. His name was Gunnar, and he worked at the Boliden mine. He died in a blasting accident in the mid-seventies."

Blomkvist's heart sank.

"But his wife is still alive. The one in the picture here. Her name is Mildred, and she lives in Bjursele."

"Bjursele?"

"It's about six miles down the road to Bastutrask. She lives in the long red house on the right-hand side as you're coming into the village. It's the third house. I know the family well."

"Hi, my name is Lisbeth Salander, and I'm writing my thesis on the criminology of violence against women in the twentieth century. I'd like to visit the police district in Landskrona and read through the documents of a case from 1957. It has to do with the murder of a woman by the name of Rakel Lunde. Do you have any idea where those documents are today?"

Bjursele was like a poster for the Vasterbotten country village. It consisted of about twenty houses set relatively close together in a semicircle at one end of a lake. In the centre of the village was a crossroads with an arrow pointing towards Hemmingen, 101/2 miles, and another pointing towards Bastutrask, 7 miles. Near the crossroads was a small bridge with a creek that Blomkvist assumed was the water, the sel. At the height of summer, it was as pretty as a postcard.

He parked in the courtyard in front of a Konsum that was no longer open, almost opposite the third house on the right-hand side. When he knocked on the door, no-one answered.

He took an hour-long walk along the road towards Hemmingen. He passed a spot where the stream became rushing rapids. He met two cats and saw a deer, but not a single person, before he turned around. Mildred Brannlund's door was still shut.

On a post near the bridge he found a peeling flyer announcing the BTCC, something that could be deciphered as the Bjursele Tukting Car Championship 2002. "Tukting" a car was apparently a winter sport that involved smashing up a vehicle on the ice-covered lake.

He waited until 10:00 p.m. before he gave up and drove back to Norsjo, where he had a late dinner and then went to bed to read the denouement of Val McDermid's novel.

It was grisly.

At 10:00 Salander added one more name to Harriet Vanger's list. She did so with some hesitation.

She had discovered a shortcut. At quite regular intervals articles were published about unsolved murders, and in a Sunday supplement to the evening newspaper she had found an article from 1999 with the headline "Many Murderers of Women Go Free." It was a short article, but it included the names and photographs of several noteworthy murder victims. There was the Solveig case in Norrtalje, the Anita murder in Norrkoping, Margareta in Helsingborg, and a number of others.

The oldest case to be recounted was from the sixties, and none of the murders matched the list that Salander had been given by Blomkvist. But one case did attract her attention.

In June 1962 a prostitute by the name of Lea Persson from Goteborg had gone to Uddevalla to visit her mother and her nine-year-old son, whom her mother was taking care of. On a Sunday evening, after a visit of several days, Lea had hugged her mother, said goodbye, and caught the train back to Goteborg. She was found two days later behind a container on an industrial site no longer in use. She had been raped, and her body had been subjected to extraordinary violence.