The main shopping street in Reykjavík is called Laugavegur, “the way of hot pools”, because it was originally used by women hauling laundry from the town to the thermal springs two miles away. It cuts across Iceland’s capital from west to east, with the Atlantic Ocean below and, above, the bone-white Hallgrímskirkja church looming over the city’s brightly coloured roofs like a tower from Tolkien’s Middle-earth. It was a street that Birna Brjánsdóttir knew well.

A vivacious 20-year-old woman with auburn hair and a sharp sense of humour, Birna grew up in the suburbs, a 30-minute walk away. She liked music – everything from hip-hop to folk – and she liked to drive, and so in the summer of 2016 she embraced the Icelandic pastime of rúntur, cruising slowly down Laugavegur in her father’s car with her friends, windows open, speakers blaring, past the boutiques and coffee bars and tourist shops selling soft-toy puffins and knitted jumpers.

That winter, when the sun appeared for only five hours a day and the snow piled deep on the nearby mountains, Birna had been enjoying the nightlife around Laugavegur. After finishing work on a Friday, she would often play cards in a pub with some friends and then, after midnight, when people in Reykjavík finally start to party, they would go dancing, as they did on the evening of 13 January 2017.

Self-assured and carefree, Birna was one of the first people that night to get up and dance on the stage at Húrra, a popular live music venue and club. When her friends decided to leave at 2am, she told them she would stay on. She left the club just before closing time three hours later. She bought a falafel pitta and started slowly walking up Laugavegur, which is brightly lit at night, with glowing storefronts and lampposts every 10 metres or so.

She was walking alone, which was not unusual behaviour in Reykjavík, even for a young woman. More so than in most other countries, Icelanders feel they know their own people; it is a peaceful place where entire years have passed without a single murder. It was -9C with the windchill, but Birna seemed unperturbed. She wore Dr Martens boots – regular black ones, not her knee-high pair with the glow-in-the-dark skeleton foot on the side – black jeans, a grey sweater and a black hoodie draped over her shoulders. Her hair hung loose and a pair of white earbuds dangled around her neck.

She was drunk, dropping coins at one point and bumping into a stranger on the pavement. She ambled past the yellow-and-red awning of the Lebowski Bar, inspired by the Coen brothers film, and a coffee-and-waffle shop on a corner where a narrow lane led down to the sea.

And then, she disappeared.

When Birna did not show up at work on Saturday morning, her friend María raised the alarm. Birna was always on time. They worked in the fashion section of the Hagkaup department store, and had known each other since primary school. They were close friends who used to watch Britain’s Got Talent and go to music festivals together. Mariá called Birna’s mobile. It was off – and Birna’s mobile was never off.

María contacted the girlfriends Birna had been out with the night before. They had assumed she had gone back to her father’s house, where she lived, but she was not there. María then called Birna’s mother, Silla Hreinsdóttir, who was worried by the news. Her daughter was independent and strong-willed, but also responsible, and always let her parents know where she was.

That evening, after filing a missing-person report with the police, Silla posted a message on Facebook, saying that her daughter had not come home from her night out or been heard from since. “Dear friends … It’s not like her that we can’t reach her. Please share and let’s find her. Silla.”

Within a few hours, the post had been shared thousands of times, but there was no word from Birna. Her mother stayed awake all night, calling the emergency services every hour, sometimes every half hour, to see if they had any news. At 9am on Sunday, there was an update from the police. Before Birna’s phone was turned off, or ran out of power, at 5.50am the day before, it had pinged a mobile tower in an industrial area in Hafnarfjörður, a port town six miles south of Reykjavík, known for its lava fields and Viking festival. Hreinsdóttir drove there with some relatives and several of her daughter’s friends, knocking on doors and calling Birna’s name.

By the early afternoon, with the light fading fast, Silla was desperate. Her daughter had not been seen for nearly 36 hours, and she was convinced something was horribly wrong, but there was still no official search. Without evidence of foul play, the police were reluctant to act. But the media had picked up the story, and when the two main television stations called requesting interviews, Silla agreed. The mystery of the young woman who had disappeared from Reykjavík’s best-known street appeared on the Sunday evening bulletins.

With a small, mostly homogenous population of 340,000 and a high degree of economic equality, Iceland is one of the world’s safest nations. It is the only Nato member without a standing army. Gun ownership is high – there are estimated 90,000 firearms in civilian hands – but the weapons are purchased for hunting rather than self-defence, and very seldom misused. Violent crime is rare. Between 2000 and 2015 there were an average of just 1.6 murders a year, with most of the perpetrators and victims young men known to each other. In 2008, there were no homicides at all. Police are not armed, and the Reykjavík force’s Instagram feed shows officers eating ice-cream, sledding and posing for selfies. The feeling of security is bolstered by Icelanders’ tendency to look out for one another, a tradition that dates back to times when close collaboration was essential to make it through the long, brutal winters.

Detective Grímur Grímsson did not watch the television news that Sunday night, but as he was finishing dinner with his wife, his phone rang. It was his supervisor, telling him about the missing woman. Soon after, he received a second call from the police headquarters in Reykjavík asking him to come in.

Although his sister, Vigdís, is a well-known novelist in Iceland, Grímsson, 56, was a private person, who liked to be, as he put it, “without a face”. In truth, he has the perfect face for a detective, raptor-like with his swept-back hair, blue eyes, stubble, sharp nose and two deep lines that frame his mouth in parentheses.

His 30 years in the police force had not been spent eating ice-cream. In the 1990s, he had been based in the northern Westfjords region, near the Arctic Circle, when several avalanches struck, killing more than 30 people. In early 2009, during the financial crash, he joined the special prosecutor’s office, and spent six years building cases against the managers and traders whose market manipulation and fraudulent loans helped bring down Iceland’s three biggest banks. Only in November 2016, having missed the “faster beat” of regular police work, had he returned to the Reykjavik force.

Driving to the police station that Sunday evening, Grímsson was not overly worried. Each month several people are reported missing in Iceland: hunters and hikers in the country’s hostile interior, youngsters running away from home or involved with drugs, people with mental health problems or Alzheimer’s, suicide victims. In urban areas, young people reported missing usually turned up quickly, after having slept at a friend’s house – as Birna often did, with her female friends – or hooking up with someone for the night.

CCTV footage of Birna Brjánsdóttir walking through Reykjavik on the night she disappeared. Photograph: Reykjavik Metropolitan Police/EPA

At police headquarters, just off Laugavegur, Grímsson was briefed on the case. Officers had collected a sample of Birna’s clothing from her father’s house, to give the scent to tracker dogs, which had been taken to the spot where she was last seen. Reykjavík had thinner CCTV coverage than many European capitals, due to the low crime rate and a hostility to surveillance and other crime-prevention measures in a society that largely polices itself. In public discussions about the need to be prepared for terrorist attacks or to tackle the underworld, a common refrain was “that kind of thing does not happen here”. But officers had been able to piece together grainy footage showing Birna’s movements after leaving the club on Saturday morning. Grímsson watched her drop the coins and bump into the stranger before walking past the Lebowski Bar. But in footage from the next camera, one short block away, there was no sign of Birna. Either she had gone down the side road, or had climbed into a passing vehicle.

Scrutinising the video again, Grímsson and his colleagues noticed a small red car, a Kia Rio, travelling in the opposite direction to Birna. It drove past the Lebowski Bar less than 30 seconds after she had appeared on camera there. Had she got into that car? It was possible, the officers thought. But the video quality was not sharp enough to identify the occupants, or the number plate. And when police checked the national vehicle database, they found more than 100 cars of the same make, model and colour.

At 2am on Sunday night, Silla and Birna’s father, Brjánn – who are divorced but on good terms – arrived at the police headquarters. Silla pleaded to be taken seriously, and for an immediate search. Birna had no reason to go missing, she insisted: she was close to her family, and was not involved with drugs, or depressed. One of her friends described her as a “happy pill” because she was invariably so upbeat. Nor did she have money worries: her income from her department store job was more than enough, she had told her mother. What was more precious was time – time spent with people she loved, and doing the things she loved.

When Grímsson showed them the CCTV footage, Silla was furious that they could not identify the red car’s number plate. “Can’t you find it, like in the movies?” she said. “It doesn’t work like that,” Grímsson replied.

The idea that everyone knows everyone in Iceland is a stretch. But mention one Icelander to another and they will probably know someone who knows them. There is a strong feeling that every person is a valuable part of the community – and that when assistance is needed, you step up. “Everybody here does things that are not paid, whether it’s singing in a choir or organising a sports team,” said Lilja Sigurðardóttir, a leading crime novelist. “It gives us an inflated sense of our own value and importance. It’s not always helpful, but it can be beautiful.”

By Monday afternoon, with no further leads, the police sought to tap into that spirit, calling a rare press conference to appeal for information that could help locate Birna or identify the driver of the red car. Despite feeling that the police were still treating her like a “hysterical mother”, Silla agreed to appear beside Grímsson, who had been assigned to lead the case. She told reporters that she feared her daughter, who loved speaking English and travelling – she and María were planning a trip to New York in two months – might have stopped to speak to tourists on her way home. She added that Birna had recently joined Tinder after breaking up with her boyfriend.

A poster appealing for information about Birna Brjánsdóttir’s disappearance. Photograph: Eggert Jóhannesson/Morgunblaðið

Grímsson gave an update on the search, which was being led by the Icelandic Association for Search and Rescue (Ice-Sar), a sprawling network of well-trained emergency-response volunteers. Its roots go back 100 years, and its continued existence reflects the reality that the main dangers in this island nation come from the harsh natural conditions rather than from other people. Generally, having ordinary citizens – as opposed to Ice-Sar teams – involved in a search for missing persons in Iceland is a hindrance, “because you have people who don’t know what they are doing”, according to Guðbrandur Örn Arnarson, the organisation’s project manager. But just a few hours after the press conference, late on Monday night, it led to a breakthrough.

Two brothers in their 20s, with no connection to Ice-Sar or to Birna, went looking for her in Hafnarfjörður, where the last signal had been picked up from her phone. On a whim, they headed to the harbour. Between the road and the sea was a fenced-off area with three large oil storage tanks, and next to it an open patch of rough ground littered with building supplies. The brothers decided to look around. Alongside some pipes, they spotted a pair of black boots. The missing-person appeal had described Birna’s clothing. The men Googled “Dr Martens” and, seeing a resemblance to the boots they had found, posted a photograph on Facebook. Officers rushed to the port. The boots, they quickly ascertained, belonged to Birna.

As divers plunged into the icy waters and drones hovered above, Grímsson’s officers pored over CCTV footage from the docks. They soon spotted a red Kia Rio entering the harbour shortly after 6am on the Saturday morning. The car parked alongside a 65-metre fishing trawler, the Polar Nanoq, sailing under Greenland’s flag. A man exited the passenger door and walked slowly, drunkenly, on to the ship. The car then drove off.

This time the number plate was legible. It was a rental vehicle, which the company said had been hired by a crew member of the Polar Nanoq, Thomas Møller Olsen, a 25-year-old man from Greenland. He had returned the vehicle at lunchtime on Saturday, and it had since been hired out again to a young family. Police impounded the car. It was obvious that it had recently been cleaned – the family’s son, sitting in the back, had complained of the strong chemical smell. On closer inspection, officers found traces of blood on the back seat. Since Iceland lacks a sophisticated forensic crime laboratory, a sample was sent to Sweden for analysis, along with Birna’s DNA.

The hunt was on for Thomas Olsen and the man seen walking from the car to the ship on Saturday morning. Unfortunately, the trawler had set sail on Saturday afternoon with both men on board.

By the Tuesday, three days after Birna disappeared, the Polar Nanoq was many hundreds of miles away, fishing off Greenland. Since leaving Iceland, Thomas Olsen and his companion from the car, Nikolaj Olsen (a fellow Greenlander, no relation), had seemed their usual selves. But then Thomas, who was described by his crewmates as likable and easygoing, received a message on his phone that made him visibly agitated. A newspaper reporter in Reykjavík, who had learned that the Polar Nanoq had been linked to Birna’s disappearance, had discovered a Facebook group used by the crew and sent a speculative message to Thomas asking if he knew who had rented the red Kia Rio. Thomas, who had gone pale, showed the journalist’s message to the ship’s captain, who told him he did not have anything to worry about if he had not done anything wrong, and gave him some sedatives.

For Grímsson’s team, the pursuit of the two sailors presented a major logistical and diplomatic challenge. A coast guard helicopter had flown four police officers to a Danish warship, the Triton. Because the Polar Nanoq was a Greenlandic vessel, in Greenland’s waters, the plan was to sail to Greenland, an autonomous territory of Denmark, collect local police officers there, and take them to the Polar Nanoq to make the arrests. Grímsson’s concern was time: the longer the suspects were at large, the more opportunity they would have to destroy evidence and coordinate stories.

Then, Grímsson received some news that allowed for a swifter and simpler solution: the captain of the Polar Nanoq, who had read online that the ship had been linked to the disappearance and was concerned his men might be implicated, had decided to sail back to Iceland. He and the senior crew agreed they would tell Thomas and Nikolaj that the engine had malfunctioned, necessitating the turnaround. The captain also turned off the wifi, so the two men would not be able to read the media reports about the case.

Though Iceland does not have special forces, it does have an elite counter-terror unit within the police, called the Víkingasveitin, or Viking Squad. Early the next morning, Wednesday, six members of the Viking Squad boarded an A332 Super Puma helicopter and flew out to meet the Polar Nanoq as it crossed into Icelandic waters. Although the weather was bad and the sea rough, with eight-metre waves, the officers safely rappelled on to the deck. Thomas and Nikolaj were arrested and confined to their cabins. In 12 hours, the Polar Nanoq would reach Hafnarfjörður.

The Polar Nanoq fishing trawler, on which Thomas Olsen was a crew member. Photograph: Eggert Jóhannesson/Morgunblaðið/Eggert

By now, all of Iceland was following the story, with an increasing sense of foreboding. Parents who had never before needed to explain the dangers of crime to their children struggled to answer their questions about the missing young woman and the sailors. In the cafes and bars of Reykjavík, people checked for updates on news sites and swapped theories about what had happened. Other instances of violent crime, rare as they were, were not mysteries that needed solving, or that required manhunts. This one was unfolding like the plot of the noir novels that have become so popular in Iceland over the past decade. “It represented the ultimate fear in our society: a young, innocent woman targeted in a downtown area,” said Helgi Gunnlaugsson, a sociology professor at the University of Iceland. “And then the suspects were outsiders – that only intensified it.”

The strong public reaction was mostly well-intentioned – passing on potential clues to the police, empathy for Birna’s family – and appreciated. The national broadcasting service, RÚV, had even postponed the airing of the second series of the BBC drama The Missing, about a girl who disappears, out of respect for relatives and friends of Birna. But with so many people playing amateur detective, wild rumours were spreading online. Late the previous night, Grímsson had sent officers to Hafnarfjörður to dispel reports on social media that a body had been found in a lake. Now there was fresh speculation: that Birna was alive on the Polar Nanoq, and that several other abducted women had also been found on board. Grímsson, whose composure, focus and openness when updating the public had endeared him to many Icelanders, appealed for calm and urged people to avoid “mob fever”.

With the Polar Nanoq just hours away, the harbour at Hafnarfjörður was sealed off to keep the public at a distance. The port was blanketed in snow, and red-and-blue uniformed Ice-Sar volunteers quietly continued their search for evidence. More than a dozen police vehicles were parked in a line on the dock with their lights on when the ship finally sailed into view at 11pm on Wednesday night.

“You had this feeling like all the police cars in Reykjavík were there,” said Snærós Sindradóttir, a reporter covering the case for Fréttablaðið, Iceland’s biggest newspaper. Viking Squad officers led Thomas and Nikolaj off the ship in handcuffs. “It was a really powerful moment,” said Sindradóttir. There was always this chance that we had lost the suspects.”

After days of unrelenting bad news about the case, Icelanders at last had a small measure of relief. That the arrested men were foreign provided an extra level of comfort to some, “a blessing that allowed us to be united as a people”, as one person put it.

The police convoy sped to the headquarters in Reykjavík, where questioning began immediately. Forensic tests in Sweden had revealed that the blood in the car was Birna’s. But both men, interviewed separately, denied causing her any harm. Their accounts of what happened the previous Friday night and the first part of Saturday morning, until Nikolaj was dropped off at the ship, were similar.

The Polar Nanoq had arrived from Denmark on 11 January 2017, a Wednesday, to pick up fresh crew members, and on the Friday, a few of the men remaining on board decided to go for a night on the town before heading back to sea. Nikolaj took a taxi from Hafnarfjörður to Reykjavík, and went for a drink in the English Pub just off Laugavegur. He paid 2,500 krona (£18) for a spin of the lucky wheel, a game of chance with a grand prize of eight beers – which he won. By the time Thomas had driven the rental car to the capital and joined his crewmate, Nikolaj was already very drunk. They later moved to another bar, before going for a drive and ending up on Laugavegur, where the red Kia Rio was captured on CCTV at the same time as Birna disappeared.

Both men claimed that two women had entered the car at that point, although Nikolaj, who said he fell asleep on the way to Hafnarfjörður, recalled nothing about them. Thomas told police that after dropping Nikolaj off at the Polar Nanoq, shortly after 6am, he had parked at the end of the harbour and climbed into the back of the tiny car with the two women, one of whom was Birna, who he claimed to have kissed. He said he dropped the women off at a nearby roundabout after about an hour.

To the police, Nikolaj’s vagueness seemed plausible – from the CCTV footage at the harbour they could see how drunk he was. But Thomas’s account was full of holes. At 7am on Saturday, when he was seen on camera driving away from the harbour, his phone went off for four hours. The car was not seen on any surveillance footage again until 11am, when Thomas returned to the port. He said he had slept in the car during that time, although the odometer reading suggested he had taken a long drive. Soon after, he was captured on video buying Ajax cleaning liquid, clothes and plastic bags at a supermarket, and then scrubbing the inside of the car.

He claimed to have been trying to remove vomit from the back seat. But after the rental car was impounded, and the blood sample taken for testing, a forensics officer sprayed the interior of the vehicle with Luminol, a chemical that glows bright blue when it comes into contact with bloodstains, even those that have been cleaned up and are invisible to the naked eye. The car “lit up”, the officer would later testify.

Other evidence also weighed against Thomas. The doctor who examined him noted scratches on his chest, indicative of a struggle. Meanwhile, officers searching his cabin in the Polar Nanoq had found 23kg of hashish, with a street value of £1.4m, which he had brought on to the ship in Denmark. More importantly, they discovered Birna’s driver’s licence, folded and discarded in the ship’s rubbish tip. The licence was sent to a crime lab in Norway for fingerprint analysis. Grímsson was certain that Thomas was responsible for Birna’s disappearance. But he was still no closer to finding her.

On the morning of Saturday 21 January, a week after she vanished, the biggest search operation in Iceland’s history began. Ice-Sar alone deployed 835 volunteers and 87 vehicles, an extraordinary response in a small country. Across the island, people waited anxiously for updates.

“Today she is our sister, our daughter – that became the mantra,” said Guðbrandur Örn Arnarson, Ice-Sar’s project manager. “We don’t live in a society where we tolerate a 20-year-old woman being abducted in the night.”

The vast search area included Iceland’s Southern Peninsula, with its lava fields, snowy hills and frozen lakes. Saturday’s search yielded nothing. Around noon the following day, a coast guard helicopter flying low over the desolate coastline neared the bright orange Selvogsviti lighthouse. There is no beach there, only a berm of large black stones littered with fishing buoys and driftwood from distant lands. Kelp bobbed in the shallows, and the rockpools were glassed with ice. An officer on board the helicopter spotted something near the water’s edge. It was Birna’s body.

Shock quickly gave way to grief. Memorials were held in Greenland, whose citizens had followed the case with horror and shame, in Denmark, and all the main cities in Iceland. In Reykjavík, thousands of people walked together down Laugavegur, leaving candles and flowers at the spot where Birna disappeared. Her funeral was held at the Hallgrímskirkja, the biggest church in the country, with the president and prime minister among the 2,000 mourners. Birna’s friends carried the white coffin. The songs included two that she had introduced to her mother in her last months: Gerry Rafferty’s Right Down the Line and You by English musician Keaton Henson: “If you must die, sweetheart, die knowing your life was my life’s best part,” go the lyrics.

For weeks, Birna’s mother was too devastated to hear the details of how her daughter had died. In March, she asked to meet with Grímsson and the chief of Reykjavík Metropolitan police, who were eager to give her some closure, and told her what they knew. Though Birna was found naked, there was no evidence of sexual assault. She had been struck in the face and strangled – at the harbour, police believe, when Thomas was seen on camera entering the back of the car, before his phone was turned off and he drove away from the port – but she was alive when she was put into the water. The autopsy revealed the cause of death to be drowning.

Birnu Brjánsdóttur’s funeral at the Hallgrímskirkja church in Reykjavik. Photograph: Eggert Jóhannesson/Morgunblaðið

Nikolaj had been released after two weeks in custody, when police concluded he was not present when the crime was committed. Despite the evidence against him, Thomas did not confess, sticking to the same story through nine police interviews. Police still had no idea why Birna got into his car on Laugavegur, or why he killed her.

On 30 March 2017, Thomas was charged with murder and drug possession. When his trial began in August, the prosecution’s case was even stronger: his DNA had been found on the laces of one of Birna’s boots, and Norwegian forensic scientists had identified his fingerprint on her driving licence.

Entering the court in Hafnarfjörður, Thomas covered his face and sat facing away from the gallery. He confessed to drug possession, but not to murder. Speaking in a low voice, and without emotion, he spun a completely new story. Instead of two girls in the car, now it was only one, Birna, who he said had suddenly climbed into the Kia Rio as he drove along Laugavegur. Thomas said he had stopped the car and got out to have a pee in Hafnarfjörður, at which point Nikolaj drove off with Birna, returning some time later without her, to pick him up. To the astonishment of everyone in court, Thomas was trying, at this late stage, to pin the murder on his crewmate. A month later, the three judges convicted Thomas of both charges and sentenced him to 19 years in prison.

Thomas has appealed against his conviction, asking the court for an independent assessor to analyse whether it was possible for him to have disposed of Birna’s body, given the ocean currents and the mileage on the rental car.

It is now more than a year since Birna died. Has her murder changed Iceland? Superficially, no. There has been little new animus towards outsiders, even fishermen, and young people have not stopped going out or getting drunk. On a clear, cold night in early March, the bars and clubs in downtown Reykjavík were busy, with British and American tourists watching Champions League football in the English Pub, and black-clad locals packing into Húrra for a heavy metal party.

But ask any Icelander and they will tell you something has shifted. “This case will be remembered,” said Vigfús Bjarni Albertsson, the chaplain who conducted Birna’s funeral. “It changed us a bit, our feeling of security.”

There are now more CCTV cameras in Reykjavík; the argument that more surveillance is unnecessary has been lost. Young women in particular are more wary – more careful, and conscious of the need to look after one another. Catching a lift from strangers after a night out had become common in recent years, especially through a Facebook group called Skutlarar (“those who give people a ride somewhere”). After Birna’s death, a female-only version of Skutlarar was established.

A memorial for Birnu Brjánsdóttur in central Reykjavik. Photograph: Kristinn Magnús/Morgunblaðið

The biggest effect may be on the national psyche. The murder coincided with a period of strong economic growth driven by outside forces: a tourism boom, an influx of migrants to take up low-level jobs, and foreign investment. “I think many people feel overwhelmed by how fast the country is changing, from a small island nation to something more cosmopolitan,” said Egill Bjarnason, a local correspondent for the Associated Press. “Birna’s death somehow encapsulated people’s unease about this new era.”

Grímsson has moved on from the first and possibly only murder case he will ever lead – one that turned him into a hero in Iceland and ensured he will never be “without a face” again. He is now based in The Hague, as Iceland’s representative at the EU’s Agency for Law Enforcement Cooperation.

I recently met him at the police headquarters in Reykjavík when he returned home for a few days. It was 5.30pm, and most of the officers had gone for the day. Grímsson walked me to his office, which he has kept, pausing along the way to point out the view of the bay and the mountains beyond.

He said he was proud of the investigation, but wishes his force had been quicker to respond to Silla Hreinsdóttir’s desperate pleas for a search for her daughter. “One of the things I have been thinking a lot about is this: should it be 24 hours to respond in missing-persons cases? Or more subjective?”

Silla did not attend the trial, and later made an appeal in the media for people not to refer to the murder as the “Birna case”. “I don’t want this evil act to be blended with her name,” she told me when we met one afternoon in her flat. “Birna was a beautiful soul. She did not deserve this.”

A picture of Birna hangs from a chain around Silla’s neck. Her focus now is keeping the positive memory of her daughter alive. In the living room, one entire wall is devoted to Birna. There is a large collage of photographs of her: as a mischievous child with pens pushed through her hair, swimming with dolphins in the Bahamas on a family holiday, on the beach in Hawaii, outside church. Next to the collage hangs the dress Birna wore to her brother’s confirmation, and beneath the photographs is her makeup table, with her brushes on top. She had often talked about moving to the US to train as a professional makeup artist for films and the theatre.

Like her daughter was, Silla is generous and warm. As the pale afternoon sun streamed through the window, she laughed loudly while watching the videos that Birna had recorded and uploaded to her YouTube channel: miming to rap songs, doing crazy dances. Birna’s cat, Dreki (“dragon”), who she loved dearly and always defended, despite its habit of terrorising the other family members and her friends, skulked around the flat.

And like her daughter, Silla speaks her mind. Stepping outside on to the balcony for a cigarette, she said she still has faith in God, but is mad at him. When she was praying for her daughter’s safe return, where was he? Although she is grateful for all the public support, she rejected an idea to have an annual memorial day in Birna’s name to promote “unity”, and dismisses the notion that some good has resulted from the tragedy.

“There was no purpose in this. It makes me crazy when people talk about the country coming together. It’s a fantasy: this beautiful country in the frozen north where everybody comes together … I don’t think it’s healthy for Iceland to think of itself as special in that way.”

• This article was amended on 12 April 2018 to correct a statistic about the last year in which there were no homicides in Iceland.

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