The patient had been in a coma for 12 days. Strange dreams were all he could remember. He dreamed he was in a red room, then a green room, and when, finally, he woke, the walls were orange. There was flame even in the paint colour, and he knew without being told that his wife was dead. He checked his hands and was surprised to find that his fingers – put back together now, bandaged – had been saved.

His children sat next to his bed while a young police officer had positioned his chair further away, towards the back of the hospital room. All of them were waiting to hear what had happened to him two weeks earlier, on the day of Australia’s worst recorded natural disaster. It would become known as Black Saturday: 400 separate fires had burned across the southern Australian state of Victoria, giving off as much energy as 1,500 atomic bombs.

Detective Paul Bertoncello had visited the ward before. The first time, the patient, Rodney Leatham, had been wearing an oxygen mask and couldn’t speak. He had burns to 40% of his body and was covered in layers of dressings. Leatham was crying, nodding and communicating with his eyes.

Now Leatham was ready to give his statement to the police, to help them piece together how the fire had started. Bertoncello turned on his tape recorder. He already knew the shape of the story.

Leatham, a carpenter, is working on his house in the town of Morwell when he sees smoke rising over Churchill, another town six miles away. He worries the fire is heading towards the tiny hill community where his daughter lives with her partner and small children. Leatham and his wife, Annette, drive over to assist in case there are spot fires. Annette is a frail woman with an autoimmune disease. She stays inside helping her daughter, while outside her husband and son in-law connect a generator Leatham has brought, in case they lose power. Then the two men fill buckets and containers with water.

Throughout the afternoon, the family listen to the radio and check the websites of the country fire authority and the department of sustainability and environment. There are now blazes all around the state, although no specific warnings are issued for their area. Outside, it is growing dark. Smoke blocks the sun and the sky glows red. They lose power: the lights and radio go off, the phone and internet stop working. Rodney and his son-in-law prepare for fire to come their way while believing it won’t. But in many minds, staying to defend your house is the Australian test of grit: it’s proof that you deserve to be living in the bush in the first place. Holding their nerve, they decide to make dinner.

In the background they can hear the blaze, constant like an ocean. Surrounded by steep gullies, they can’t see flames and can’t tell where this fire is, until suddenly it feels very close. The family debate whether to stay or go, stay or go, and then it is clear they had only moments to leave.

Leatham’s daughter and son-in-law drive away first, in separate cars. But a beast has found them: at the end of the driveway, a spot fire ignites in the next paddock. Then, all at once, burning debris falls everywhere, along with fat drops of black rain. This fire is now creating its own weather system. His daughter is driving underneath a pyrocumulus, a massive grey fire cloud that has formed over the smoke plume. Hot air has risen in a convection column, and as the cloud grows heavy, it rains – pointless, ironic drops.

Black splodges of liquid soot fall over the windscreen, the wipers now cutting up the view of fire everywhere. Native animals come down the road, fleeing a burning fauna reserve. In the first car, Leatham’s son-in-law hits a kangaroo, then his daughter hits it, too. In the chaos, she realises her parents aren’t behind her. At the top of a hill she stops, debating whether to return to her parents or go on towards her children.

Now, in this room full of medical equipment, Leatham is telling them what happened at the house. His children ask no questions. They cry as he describes going to disconnect his generator, he and their mother getting into the truck and finding they are surrounded by flames. Bertoncello’s tape recorder stops working and he starts transcribing Leatham’s words into his notebook as fast as he can:

“This is where everything turned into milliseconds. Everything is slow.

“The fire … the fire was coming over the hill. In the next millisecond, no sooner had the ute stopped, Annette tells me: ‘Let’s run to the house.’ She opens the door. There is no time to say yes or no. It’s just what we’re doing. She turned out of the car, out of the passenger door and fell over. I heard her cry out. I got out, ran around the car and she was virtually on fire. I tried to drag her. She was in flames. I was putting my hands in flames, but I couldn’t hold on. It was so hot. I couldn’t do anything. I looked around. Shrubs were like glow bombs on fire. I wanted to help her … there was nothing I could do.

“I knew I had to move, to run to the house. The flames were head height from the ground. I don’t know how I got there … I sat in a child’s plastic sandpit shell filled with water, and cursed everything under the sun.”

Bertoncello wrote this down through tears. He had seen the aerial photographs of the crime scene. The house had somehow remained untouched. It stood there ringed by burned earth, the truck sunk in postnuclear ash. Nearby was the dam – from the sky, just a pockmark – to which Leatham had run from the plastic sandpit and submerged himself. Lying low, in a grief-filled hallucination, he had seen the eucalypts “glowing like Christmas trees, like somebody had put a massive amount of fairy lights over trees 30 metres tall.”

On the evening of Black Saturday, Detective Adam Henry had been called back from paternity leave for a 6am meeting the next morning. Everyone in the Victoria police arson and explosives squad was called back. The previous few days had been implausibly hot, with Saturday the endgame – mid-40s C (113F), culminating in a killer 60mph northerly wind. That afternoon and throughout the night, firestorms had ravaged areas to the state’s north, north-west, north-east, south-east and south-west. Henry was sent two hours east of Melbourne to supervise the investigation of the Churchill fire, which had started about two miles away from the town itself. The investigation was named, for obvious reasons, Operation Winston.

At first, units of detectives, forensic scientists and crime-scene experts were deployed to different regions – the standard response. But the devastation was on a scale that could be envisaged only by those with training in counter-terrorism. Blazes believed to have been ignited by failing powerlines and arson had burned 450,000 hectares (1.1m acres). Days after the fires had begun, there were areas around Victoria that still couldn’t be reached, and in areas that could, corpses were everywhere. The army and emergency services were finding the bodies of those who had sought shelter to no avail by the sides of roads and under bits of tin that were formerly houses. It would take weeks to establish that, altogether, 173 people had been killed.

Facebook Twitter Pinterest A Victoria bushfire rages. Photograph: Getty

On Sunday 8 February, Henry and a colleague drove through the smoke along the motorway to the Latrobe Valley. On the radio, the death toll was still rising – 50 people, then 100. Whole towns, it was reported, had burned to the ground.

Henry turned off to Churchill, a mile or two south of the highway. The town, built in the late 1960s as a dormitory suburb for electricity workers, had wide streets and a slender, anodised statue rising 30 metres out of the ground. It was the sole public monument, commemorating the great man of Empire in the form of a stylised golden cigar.

The detective didn’t stop. He could see smoke above the blackened hills circling the town and wanted to get to the fire’s suspected area of origin before it was disturbed. If this was a case of arson, the police needed to prove the connection between the point of ignition and the victims, some of whom were likely to be miles away, in places still too dangerous to access.

After passing the final roadblock, Henry parked. Out of the car, it was eerily quiet. No birds cried, no insects thrummed their white noise. The air was cool, pungent with eucalyptus smoke.

Ross Pridgeon, a local wildfire investigator from the department of sustainability and environment, had been the first to examine the scene that morning. Among the precise rows of smouldering blue gums, he had found signs of two deliberately lit fires, 100 metres apart.

Pridgeon showed the assembled police team how he had traced his way to the place where the two fires joined. Three-hundred metres along the outlet, flames had crossed from the east side to the west, high up, flashing in the tops of the trees. This was where a head fire – one of the two burgeoning fire fronts – had come surging through. The eucalypt crowns had been stripped out and the remaining blackened leaves appeared stiff, snapdried, arrowing in the direction of Saturday’s wind. The gum leaves, pliable up to a certain temperature, were like thousands of fingers pointing the way the fire had gone: a sign to the investigators that if they entered the fire zone here and moved back in the opposite direction, they might come to where it started.

The ash-covered ground crunched underfoot. Henry trod carefully to minimise disturbing what could be evidence. This blaze had been so intense that the aftermath was like stepping into a textbook on wildfire investigation. Heat was rising off the burnt trees and smoke hung low around the boughs. Henry and the others navigated their way through this smoke, following the subtlest of signs.

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Tens of thousands of hectares of plantation, state forest and private property had been burnt and yet, after an hour studying and photographing the evidence, the men could tighten their flags into an area of eight square metres, marking the outline of where it seemed the fire had been lit. There was no sign of an incendiary device, but in the explosive conditions of the day before, all the arsonist would have needed was a lighter. One flick of the finger and the spark wheel releases terror.

The second fire had started only a short walk from the first. A local police officer had found Pridgeon earlier in the day and told him the initial crew attending the blaze had seen two parallel fires burning.

This second fire appeared to have started just behind a sign reading “Prohibition Against Dumping”, regarded locally as an invitation to unload rubbish. There were three bicycles, or the twisted remains of their frames, alongside the burnt debris of old tyres and other car junk, televisions, mattresses, couches, a pram, children’s toys – the domestic excess of people unwilling or unable to pay fees at a tip. None of it was the kind of rubbish that could self-ignite.

The evidence suggested that two high-intensity head fires had moved rapidly south-east, fan-forced by the hot, strong north-westerly. They had been separately lit, in conditions ideal for a monster blaze.

Twelve years of drought had turned the logs in the plantation’s undergrowth, the leaf litter, and even the organic matter in the soil, into fuel. The arsonist had had no need to set kindling among the blue gums. Each tree had made its own pyre. Every summer, they dropped their bark and branches and leaves, and each year without fire the piles grew higher, and they released toxins to ward off new growth that would compromise their fuel beds. No plant on the planet craves fire like the eucalypt: to live it needs to burn. “Gasoline trees,” the Americans call the Eucalyptus globulus. Flames release gases that act like propellant, sending fireballs rolling across treetops. The shedding ribbon bark unfurls streamers of fire that travel miles on the wind.

The fire scientists weren’t about to speculate on who had lit this fire. When they turned up to a job, they didn’t want to know the local rumours about Firebug X or Y. Nothing but the uncannily expressive evidence concerned them.

Henry’s job, however, was just beginning. It is estimated that only 1% of bushfire arsonists are ever caught. As he got closer to the site of the first flame, it felt as if he moved further away. As the scientists inspected the ground for signs of whatever the arsonist had used to start the fire, Henry stood and wondered: “Why?” Surely whoever did this had known that on such a day a blaze would likely cremate everything in sight? Or was knowing this the reason?

For all the science, Henry knew that arson was a crime about which the arson squad – like everyone else – knew very little. Through the years, various agencies have tried to establish criteria for profiling firesetters. But most international studies focus on the deliberate ignition of houses, cars and buildings, rather than wildfire arson – a form of fire-lighting that, although not unique to Australia, is a national specialty. Of vegetation fires in this country, 37% are deemed suspicious and 13% maliciously lit.

Henry knew the basic hypotheses of the FBI and various other profiling systems, and was conscious that some were fairly complicated. One prominent model used this equation to explain the behaviour: firesetting = g1 + g2 + e, where [e = c + cf + d1 + d2 +d3 + f1 + f2 + f3 + rex + rin]. What the sum tended to find was that firesetters were more often than not male; they were commonly unemployed or had a complicated work history; they were likely to have disadvantaged social backgrounds, often with a family history of pathology, addiction and physical abuse; and many exhibited poor social or interpersonal skills. It was a plausible profile, but hardly different from that of many non-firesetting criminals. In other words, close to useless.

As the detectives began talking to witnesses, one particular name kept coming up. He had been near the location where the fire had started at roughly the time where it started, and multiple witnesses had described seeing him act strangely that day.

Facebook Twitter Pinterest Firefighters near Labertouche, Victoria on Black Saturday in 2009. Photograph: William West/AFP/Getty Images

The suspect, Brendan Sokaluk, had grown up only a few kilometres from where the fire began. He was 39 years old. He was single. He was unemployed and on a disability pension.

For 18 years he had worked as a groundsman at the local Monash University campus, but two years earlier he had taken stress leave and hadn’t returned. Now he supplemented his pension by delivering the local newspaper, for five cents per copy, and collecting scrap metal.

Later, the police heard about Sokaluk’s odd behaviour from his neighbours. He lived in an estate of modest houses, built in bulk in the 1970s and 80s for power-industry workers. One woman, when she moved next door to him, had been warned to keep her distance because he was “different”. He would stand staring in at her garden, then duck down and hide, not wanting to be seen himself. A few times she found him looking in with a camera. She was with her young child and told him to get lost.

The woman would hear Sokaluk banging away in his shed, pulling apart some bit of junk he had collected. He would be listening to narrated episodes of Thomas the Tank Engine or Bob the Builder – the former with their stern morality tales, the latter about high-spirited teamwork. For a while, she assumed she could also overhear him talking to a child – his speech was loud, with the detailed rolling commentary she might give her son. It was his dog, she realised. He had bought the animal when he had a girlfriend living with him, a sweet-faced, guileless woman who seemed to be gone now.

Sokaluk, it turned out, also liked to go online and chat to people. On his Myspace page, he claimed: “I’m a young happy male who wants to meet a young loven female to marrid … I don,t read books because they put me to sleep. My heroe is mother earth without her we would all be dead.” On another social media site, myYearbook, he had posted that he was “looken for a young wife to shear my wealf with her”. But on the Wednesday, four days before the fire, he had logged on and, in the third person, described his mood as “dirty”, because “no one love him”.

Facebook Twitter Pinterest A burnt-out forest in Kinglake after the Black Saturday fires. Photograph: Luis Ascui/Getty

Sokaluk had no criminal record, but it turned out that in the past he had been the subject of intelligence reports. While Henry was out investigating the crime scenes, Bertoncello pulled them up. Two years earlier someone from the Country Fire Authority (CFA) had notified police that when Sokaluk tried to join up as a volunteer his demeanour was strange. Another report suggested that fires had been previously lit on Glendonald Road, where the Black Saturday fire had started, using teepee-style configurations of leaves and twigs. On one such occasion, Sokaluk’s blue car was seen driving past the next day: had he been checking out his handiwork?

An investigator was sent to speak to Peter Townsend, a no-nonsense farmer who allegedly knew Sokaluk. Townsend was not surprised to see the police. The fire had started less than a mile from his cottage. Townsend had walked outside and seen flames twice as high as the tallest gum trees on the hills, west of his house. He and his wife had sprinted to reach their car, and as they were evacuating he recognised Sokaluk’s car in the chaos. It was parked at a strange angle. What was Sokaluk doing out, he wondered, on a 47C day? Townsend had his suspicions.

The day after the fire, Townsend found a message on his answering machine, which he now played to the investigator: “Peter, it’s Brendan. I tried to get up, see if you’re alright. My car broke down in Glendonald Road and it’s torched now. I helped one of your farmer mates last night. Tried to get hold of you, but you were busy. I’ll catch up with you later, mate. Hope you’re safe and well.’

Townsend hadn’t been expecting Brendan that day, and when he saw his car he recalled the rumours he had heard about him – rumours of smoke appearing in places Brendan had just been. The car was parked oddly. Then Townsend had seen Sokaluk himself. It was some time before 2pm. He was getting into the car of a woman called Natalie Turner.

The investigator now visited Turner, an artist, who had been lunching with her parents on Glendonald Road when the fire began. She was introducing them to a new boyfriend, Dane Carozzi. Just after their meal, she heard a helicopter overhead and looked outside at a mushroom cloud of smoke. She and her boyfriend rushed her children into the car and started to leave, but a blue vehicle that had apparently broken down partially blocked the road. A man stood nearby with his dog, looking dazed. Carozzi urged him to join them: the fire was now perilously close.

“I hope my car doesn’t burn,” the man had said when they were finally driving away. He repeated this to himself. When they dropped him home, he said it again, before adding, almost as an afterthought: “Oh, and I hope nobody gets hurt.”

Natalie Turner calculated that she had left her parents’ place around 1.45pm, placing Sokaluk a little closer again to the time of the fire’s start.

Facebook Twitter Pinterest Brendan Sokaluk in 2012. Photograph: Joe Castro/EPA

This was all coming together very quickly – almost too quickly, Bertoncello thought. It had seemed likely that the investigators would be in for a long haul, with hundreds of names thrown up and months spent scouring each blind alley, analysing every red herring. That was how it normally worked. Surely the very first person they were narrowing in on couldn’t be the one?

Bertoncello tried to dampen down an instinct saying “It’s him”. It can’t be this easy, he told himself, something’s not right. He was looking now for the catch, the evidence to eliminate Sokaluk. But each attempt to find it seemed to lock the suspect in further. It’s him.

Bertoncello looked over his colleague’s shoulder as he scrolled through emergency services records. He felt a shiver of recognition. “Hang on,” he said. “What’s that?” It was the calling line identification data, which listed callers reporting the fire. Each telephone number included the address at which the account was registered. The address paired with the second caller was the house where Brendan Sokaluk lived. It appeared that Sokaluk had rung emergency services at 1.32pm, informing them of the blaze. He must have been right there. Right at the start.

Adapted from The Arsonist: A Mind on Fire by Chloe Hooper, published on 30 May by Scribner UK and available at guardianbookshop.com. It is out in Australia through Penguin Random House

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