FJELLHAMAR, Norway — Her last phone call was at 9:14 a.m., around the time that her husband, one of the richest men in Norway, passed under the security cameras at the gates of his energy and property investment company. Not much later that morning more than 18 months ago, Anne-Elisabeth Falkevik Hagen, 68, vanished from her house in suburban Oslo.
When the police in Norway investigated, they found only a plastic strip, a shoe print and some blood stains, as well as Ms. Hagen’s cellphone. The couple’s new puppy was locked in the bathroom, and on their bed lay a poorly written, but highly detailed, ransom note asking for $9.5 million, to be paid in an obscure cryptocurrency called Monero.
At first, the police treated the matter as a straightforward kidnapping and ransom case, and they asked the Norwegian news media to remain silent. After a few months, however, the police became increasingly convinced that the clues they found in the house had been planted to mislead them and hide the fact that Ms. Hagen was actually murdered.
That growing conviction led the police in January 2019 to let the public in on the secret, in the hope that someone, somewhere could shed light on what had happened.
It is not clear whether anyone did, but the revelation electrified the nation. Late last month, the case took another sensational turn when Ms. Hagen’s husband, Tom Hagen, 70, was arrested on suspicion of having orchestrated her killing.
But without a body, a murder weapon or a clear motive, the police were forced to release Mr. Hagen a week later on the order of Norway’s Supreme Court.
From the moment it was revealed, Ms. Hagen’s disappearance — and possible killing — has gripped this Scandinavian nation, where murders are rare and crime is mainly a subject for fictional TV series and books.
Along the way, it has propelled a jazz-loving police detective into unwanted fame, with his every move picked apart by two hotshot investigative reporters. Above all, it has turned into an obsessive national whodunit, with most people suspecting Ms. Hagen’s husband of nearly five decades of being the culprit.
“We’ve never seen anything like this in Norway,” said Leif Lier, a former Oslo police chief known for recovering Edvard Munch’s “Scream” after the painting was stolen in 1994. “I follow every twist and turn, every development.”
On the day of the disappearance, Oct. 31, 2018, Mr. Hagen returned home from work around lunchtime to find the ransom note. His wife’s cellphone showed an unanswered call by an electrician at 9:48, placing the time of her disappearance sometime before then, the police said. Employees have confirmed that Mr. Hagen was at work at the time at his office complex, eight minutes from the house.
Mr. Hagen, who is worth around $190 million, made his fortune as a founder of a utility company, Elkraft, which serves all of Scandinavia. He also owns a large ski resort and other properties.
It emerged early on that in 1993, the couple, who have three grown children, changed their marriage contract, public records show, to stipulate that in the event of a divorce, she would get only the furniture, a car and the right to keep the land she inherited from her parents.
At first, that seemed to eliminate financial considerations as a motive for Mr. Hagen to kill his wife. But legal experts quickly raised doubts that the agreement would hold up in court.
Mr. Hagen’s lawyer, Svein Holden, said that the couple had not been experiencing any marital turbulence at the time she vanished.
“Throughout the marriage there have been moments that have been tough,” he said, “but they didn’t have recent problems.”
Mr. Hagen, who denies any involvement in his wife’s disappearance, suggested to the police that he might have made enemies who might have wanted to hurt him by hurting his wife, his lawyer said. If he had such enemies, though, he was certainly casual about security arrangements.
The family’s modest house on a cul-de-sac outside Oslo has no security cameras, and visitors can walk straight up to the door. Their neighbor, Rolf Arne Letvik, said he and Mr. Hagen both built their houses in 1980.
“Our children grew up together here,” Mr. Letvik said, adding of Ms. Hagen: “She was such a kind, friendly and outgoing person.”
Mr. Hagen’s address and private phone number can easily be found online, though he is something of a technophobe. He never goes near a computer, is unable to write an email and keeps the access code of his old Nokia phone scratched on the screen, his lawyer says.
In the weeks following the crime, well before Mr. Hagen became a suspect, the family and the police had conducted negotiations with the purported kidnappers, communicating through small sales of bitcoins. Different payments corresponded with different requests and answers.
After the initial contact, though, weeks would go by without anyone hearing from the supposed abductors. Finally, frustrated by the slow pace of the investigation, the police decided to permit news outlets to report what they knew. Still, the investigation went nowhere.
In July, Mr. Hagen transferred a little over $1 million to the supposed kidnappers on the promise that they would provide proof that Ms. Hagen was still alive. But none was forthcoming.
The investigation was being led by a fourth-generation police officer, Tommy Broske, who presided over a team of 200. Mr. Broske, 42, who in his free time plays drums in a jazz band, the Whereabouts, had made a name for himself policing Norway’s wild border with Sweden, squaring off with drug smugglers and a motorcycle gang, the Bandidos.
But he said last year that this was “the most demanding case I ever investigated,” all in the glare of a national obsession with the mystery.
Working methodically despite the pressures, Mr. Broske started eliminating potential scenarios. Suicide was ruled out, as was Ms. Hagen’s just deciding to flee. In either case, the police reasoned, why would she leave such a complex ransom note and have someone pose as a kidnapper and negotiate with the police and the family?
“They investigated the kidnapping until early this year; they couldn’t rule it out,” said Adne Husby Sandnes, who with his colleague Gordon Andersen has dominated reporting on the case. “But when the police were sure there never was a kidnapping, they went for the arrest.”
“Statistically most often it’s the husband,” Mr. Sandnes added. “But this case has always been surprising.”
He and Mr. Andersen, his colleague at the Norwegian newspaper VG, are sort of an odd couple. Mr. Andersen, 48, has five children and is covered in tattoos, while Mr. Sandnes is 26 and drives a 2000 Porsche 911. But they have scored several scoops in the case, revealing the contents of the ransom note, the million-dollar payment Mr. Hagen made and the amount of the ransom the supposed kidnappers originally demanded.
Finally, late last month, as Mr. Hagen was driving to work, several police cars forced him off the road and officers arrested him.
“After 18 months of investigation, the police have come to a point where we believe there is sufficient cause to suspect Tom Hagen of the homicide or complicity in the homicide of Anne-Elisabeth Falkevik Hagen,” Mr. Broske said in a statement.
“We now believe there was no abduction and that there were never any genuine negotiations,” he said in the statement. “In other words, we believe that there was a clear and well-planned attempt at misleading the police.”
A local court confirmed the arrest warrant, placing Mr. Hagen in custody. But then the Supreme Court ordered his release.
“There were no reasonable grounds for suspicion of my client, two out of three judges ruled,” Mr. Holden, Mr. Hagen’s lawyer, said.
The police tried to rearrest Mr. Hagen the same day, May 8, but that failed. Then they came up with a new suspect, a cryptocurrency expert who has not been identified in the Norwegian news media. He was released two days later, but was charged with assistance to kidnapping.
“This is simple. He wanted my client to invest, and my client didn’t do this,” said Mr. Holden. He added that he was wondering why the police were not devoting more resources to finding Ms. Hagen.
“The police are in a tunnel,” he said. “They are unable to see anything but Mr. Hagen.”
For now, Mr. Broske’s investigation has stalled, but he said he was determined to break the case.
“Our goal is still to find Anne-Elisabeth Falkevik Hagen,” the prosecutors wrote in a statement after Mr. Hagen was released. “We want to find out what happened to her and who has a role in the case.”