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Secret Bunkers and Sex Contracts: A Horrifying History of Swedish Kidnappings

Kidnappings might not be that common in Sweden, but when they do happen, they're pretty fucked up.
From the Swedish Police preliminary investigations of the Martin Trenneborg case.

This article was originally published on VICE Sweden

Kidnappings might not be that common in Sweden, but when they do happen, they are pretty fucked up. So much so that Stockholm syndrome, a peculiar phenomenon in which hostages develop positive feelings toward their captors, was named after a hostage situation that took place in Stockholm in the 1970s.

The latest kidnapping to take place in Sweden was made public in September 2015. On the evening of September 18, 37-year-old Martin Trenneborg entered a police station in central Stockholm alongside a woman in her early 30s. After briefly speaking to the receptionist, the pair sat down in the waiting hall. Two hours later, the woman was called into an interrogation room. The man stayed in his seat. Then four police officers came out and arrested him, marking the climax of a disturbing news story that the tabloids dubbed "The Sex Bunker Doctor" and "Swedish Fritzl." The chain of events included a sound-proof bunker, poisoned strawberries, and a sex contract. But more on all that latter.


On February 23 this year, a Swedish court sentenced Trenneborg to ten years in jail for kidnapping. Ever since the story broke, several criminology experts have stated that this case is one of the most disturbing in Swedish criminal history. In recognition of this alarming milestone, we assembled a brief history of Swedish kidnappings.

The Gevalia Daughter

The first case of kidnapping in modern Sweden took place in 1963—at least as far as we know. Ann-Marie Engwall, the seven-year-old daughter of Jacob Engwall, the managing director of Gevalia (Europe's largest coffee roasting company at the time) was abducted on her way to school. The kidnappers, a man and and woman who remained anonymous, claimed they were going to drive her to a school trip she had just missed.

To pass the time while waiting for the ransom money (a sum of about €1,500 [about $1,645 USD], which they apparently needed to fund their own private detective agency), the perpetrators took Ann-Marie to a petting zoo and to a café. As soon as the ransom was collected, the kidnappers put Ann-Marie in a taxi to be sent to her parents. Not wanting to go by herself, and unable to grasp the concept of abduction, she tearfully asked the kidnappers to join her.

Mr. and Mrs. Engwall contacted the police right after their daughter arrived. The kidnappers turned themselves in that same day. They would do well later in life, however. Once they served their sentences, they got married, and they had successful careers within governmental organizations.


The Girl in the Box

The kidnapping of Swedish Olympic equestrian Ulrika Bidegård took place in 1993. Swedish carpenter Lars Nilsson, who had worked on renovating the Bidegård family home, attacked her outside her parents' house in Belgium. He tied her up, gagged her, and sedated her with paint thinner. On the way up the stairs to his apartment in Brussels, he dropped Bidegård on her face, busting her lip. Once inside, she was forced to wear a blindfold and noise-canceling headphones, and she was tied sitting up inside a homemade, wooden portable toilet stall. During the four days she was held captive, she was given little food and water.

Belgian police managed to locate Nilsson after he used Bidegård's credit card to make cash withdrawals. They raided his apartment two days later, arrested him, and liberated Bidegård from her wooden prison.

A ransom letter arrived at the Bidegård estate the day after Nilsson's arrest, enclosed with a photograph of Ulrika inside the box, demanding $500,000. During the investigation, people close to Nilsson described him as kind and sound, without criminal inclinations.

The Westerberg Case

In 2002, a guy posing as a flower delivery man kidnapped Erik Westerberg, son of a successful business executive, from his home in Stockholm. Westerberg had been featured at the top of a list of wealthy youths that had been published in an evening paper that same year. Westerberg was also put in a box, and he was then transported to a cottage on an island outside of Stockholm, where he was chained to a bed.

The kidnappers demanded that about €1 million [$1,102,240 USD] in cash was attached to a wire under a bridge outside of Paris. Westerberg's father delivered the money personally. Soon thereafter, the kidnappers released Erik and gave him a pack of cigarettes and some matches. The Swedish Task Force found him after he had smoked roughly three cigarettes. Once his identity had been confirmed, Swedish police notified their colleagues in France, and shortly afterwards, French police arrested the two accomplices who had received the ransom.


The box where Fabian Bengtsson was held. Photo via Swedish Police

Another Person, Another Box

The box is a recurring theme in Swedish kidnappings. On the morning of February 3, 2005, Fabian Bengtsson was found in a park in Gothenburg, having just been released by his abductors after 17 days in captivity. "Start walking, you are free, don't look back" was the last thing the kidnappers told him before they let him go.

Bengtsson, heir to SIBA, one of the leading Nordic chains for consumer electronics, was attacked with tear gas in his garage, crammed into an empty TV box, and brought to some kind of hovel. Once there, he was transferred to another soundproof wooden box with a mattress inside. The kidnappers had targeted him in an attempt to extort about €5 million [$5,511,200 USD] from the Bengtsson family.

Over time, however, the kidnappers grew to like the abductee. When they weren't threatening him with a homemade gun or shoving balls of tape into his mouth, they cooked him omelettes and washed his clothes. They also drank whiskey and played cards with him. After a little more than two weeks, overtaken by sympathy, they released Bengtsson. They were caught by the police thanks to the many mental notes Bengtsson took while in captivity, such as at what hours he heard the sound of the ice-cream truck turn the corner onto their street, and how long it took the kidnappers to get food from McDonald's.

Bad Students

Alexander Åhman, another son of another wealthy businessman, disappeared from his student dorm in Uppsala a few days after Christmas in 2011. His abductees were his housemate, a psychology student (her presumed boyfriend who was a medical student), and one more of their friends. After the flatmate had treated Åhman to a pie containing sedatives (the pie was bitter apparently, but he ate it anyway to be polite), the kidnappers taped him up, put him in the back of a van, and drove 354 miles to an abandoned school building in the city of Umeå.

Åhman spent his week in captivity in a dark, unheated basement with very little food —beer was his only source of nutrition—and only a thin mattress to sleep on. It was very cold, so Åhman tied diapers he found in the room to his feet to retain some warmth.


Four days after the kidnapping, two of the kidnappers were in the vicinity of Stockholm. The pair had taken Åhman's mobile phone in order to text his family, posing as him. Using the "Find My iPhone" app, the family traced the phone, noting that it moved north on the highway. The police caught the kidnappers with the help of the app, and Åhman was rescued two days later.

The image above is the copy of a sex contract found in a folder called "Master Plan" on Trenneborg's computer. It made headlines due to its sadistic nature.

The Sex Bunker Doctor

Some time in 2010, Dr. Martin Trenneborg allegedly began building a faux machine shed next to his country home, in Knislinge in southern Sweden. Inside the shed, he constructed a 645 square foot, soundproof concrete bunker with double security doors equipped with electronic locks.

Five years later, in September 2015, Trenneborg went on a date with a woman, in her apartment in Stockholm—342 miles from Knislinge. He stayed for two hours, during which they chatted and had sex, and then he suggested that they meet again in two days. She accepted. He went back to Knislinge that same evening to prepare.

On their second date, they drank champagne, and he fed her Rohypnol-laced strawberries. Once she was intoxicated beyond comprehension, he handed her a diaper that she put on herself. He then fetched a wheelchair from his car, rolled her out, and put her in the passenger seat. Throughout the seven-hour drive, he injected her with sedating drugs on the hour. The woman's only memory after eating the strawberries was waking up in the car and noticing a heart rate monitor clipped to her finger.

She woke up in Trenneborg's bunker. He allegedly said that she was going to stay for a few years, cooking for him, hanging out, and having unprotected sex two or three times a day. He took samples of her blood and vaginal swabs, so he could test her for STDs, and he gave her birth control pills. He also said he was considering abducting another woman to keep her company—possibly her mother.

Five days after the abduction, Trenneborg left for Stockholm to pick up a few things from the woman's apartment and to attend a U2 concert. When he came home the next day, he offered to drive her back to Stockholm to get some of her stuff. At this point, the police had left a note on the woman's apartment door, stating that she was missed by her family, and her locks had been changed by the police.

During the trip to Stockholm, worried that police were on to him, he coached her to pretend that they were a couple. He said he didn't want to go to jail. The fact that she was being compliant and had not attempted to escape made him hope she would not report him. The pair arrived to the police station in central Stockholm, and it was not until she was separated from the man that she told the police officers what had happened to her.

On February 23, Martin Trenneborg was sentenced to ten years in prison for kidnapping. He also has to pay the woman a penalty of €19,000 [$21,000] in damages. Trenneborg admitted to kidnapping her, but he denied—and was acquitted—of a rape charge.