Picture a fairytale’s engraving. Straight black trees stretching in perfect symmetry to their vanishing point, the ground covered in thick white snow. Woods are dangerous places in such stories, things are not as they seem. Here, too, in this timber plantation, menace lingers. The blackened trees smoulder. Smoke creeps around their charcoal trunks and charred leaves. The snow, stained pale grey, is ash. Place your foot unwisely and it might slip through and burn. These woods are cordoned off with crime scene tape and guarded by uniformed police officers.

At the intersection of two nondescript roads, Detective Sergeant Adam Henry sits in his car taking in a puzzle. On one side of Glendonald Road, the timber plantation is untouched: pristine Pinus radiata, all sown at the same time, growing in immaculate green lines. On the other side, near where the road forms a T with a track named Jellef’s Outlet, stand rows of Eucalyptus globulus, the common blue gum cultivated the world over to make printer paper. All torched, as far as the eye can see. On Saturday February 7, 2009, around 1.30pm, a fire started somewhere near here and now, late on Sunday afternoon, it is still burning several kilometres away.

Detective Henry has a new baby, his first, a week out of hospital. The night before, he had been called back from paternity leave for a 6am meeting. Everyone in the Victoria Police Arson and Explosives Squad was called back. The past several days had been implausibly hot, with Saturday the endgame – mid­-40s Celsius, culminating in a killer hundred­-kmh northerly wind. That afternoon and throughout the night, firestorms 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 this fire that started four kilometres from the town of Churchill (pop. 4000). An investigation named, for obvious reasons, Operation Winston.

Through the smoke, and in the added haze of the sleep­-deprived, he drove with a colleague along the M1 to the Latrobe Valley. On the radio, the death toll was rising – 50 people, then 100. Whole towns, it was reported, had burned to the ground. The officers hit the first roadblock an hour out of the city. The dense forest of the Bunyip State Park was on fire, and the traffic police ushered them past onto a ghost freeway. For the next hour they might have been the only car on the usually manic road.

Outside, a string of towns nestled in the rolling green farms of Gippsland, and then it changed to coal country. Latticed electricity pylons multiplied closer to their source, their wires forming waves over the hills.

Turning a corner beyond Moe, Henry saw the cooling towers and cumulus vapours of the first power station, then, round the next bend, a valley ruled by the eight colossal chimneystacks of another station called Hazelwood. A vast open­-cut coalmine abutted the highway. Layers of sloping roads descended deep into a brown core – the carbon remnants of a 30­-million­-year-­old swamp – where dredgers, shrunk by a trick of the eye to Matchbox versions, relentlessly gouged the earth.

He turned off to Churchill, a few kilometres 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 kilometres away in places still too dangerous to access.

Passing the final roadblock, Henry parked and sat looking at the Nordic dreamscape on one side of the road, and the blackness on the other – the axis where the world had tilted.

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. A not unpleasant smell. On the other side of the police tape, Henry saw the police arson chemist.

George Xydias had slightly hunched shoulders and a slant to his neck as if from his many years looking for clues in ashes and rubble. He had investigated accidental fires and deliberate fires; explosions in cars, boats, trucks, planes; and, after the terrorist attacks of 2002, nightclubs in Bali. He had been to so many scorched crime scenes he could smell what type of vegetation or building material had just been incinerated, and even – to the irritation of those in his laboratory, exposed by his meticulous ways – the percentage of evaporated fuel sometimes left behind.

Wearing disposable white suits, Xydias and his assistant were talking with Ross Pridgeon, a bespectacled, shy, dryly humorous man with a mop of shaggy brown hair. Pridgeon, a local wildfire investigator from the Department of Sustainability and Environment, had been the first to examine the scene that morning. Amongst the precise rows of smouldering blue gums, he’d found signs of two deliberately lit fires, a hundred metres apart on either side of Jellef’s Outlet.

Pridgeon showed the assembled police team how he’d 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, snap­-dried, 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. He was 36 years old, handsome, with an athlete’s build and sinewy walk. He’d been selected to play football professionally but a bad injury changed his course. Later, as a detective in the transit unit, dealing with rapes and assaults on public transport, he’d one day been called to a train station that someone had set alight. Standing in the seared crime scene, Henry was impressed that the Arson Squad uncovered a chain of logic in the ash. He applied for a transfer and spent the next few years learning what fire could do, and what answers might be found in its ruins.

This blaze had been so intense 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.

Fire is a strange craftsman. It can bevel branches, blunting the wood on the origin side and tapering the back as it advances; it can “crocodile” a tree’s bough, leaving charcoal scales on the point of impact. White ash is the hallmark of complete combustion, and objects directly hit may appear lighter; a fence the men came upon had more of this pale soot on one side, and they moved further that way. Rocks and larger tree limbs often shield finer fuels, such as twigs: where the latter were unburnt, the men knew to move in the opposite direction. They looked for how deeply the timber was charred, and also at the angle of char, another sign of which way the fire had travelled – the scorch pattern on a tree trunk facing the fire’s origin was low, whereas there was a steep angle to the burn mark on the sides and back of the trunk as the flames leapt forward.

Now the investigators started walking sideways across the path of the head fire until they found indications of the fire’s flank. On the periphery of the blaze, trees were not as badly burnt: fuels that the fire’s centre would have destroyed were sometimes barely touched. The men crossed back again and found the fire’s other flank. Zigzagging back and forth, narrowing in slowly, they followed a natural V­-shape to its point and came to what is known as the area of confidence. Here, paradoxically, the signs were more bewildering. The leaves did not all angle in the same direction: in its coiling infancy, the fire hadn’t yet established its course. The damage was closer to the ground. Objects had burned in jagged ways. Somewhere very near here the fire had begun.

Beyond this area were clear signs of the backing fire, or heel fire, where the fledgling flames had reared back, trying to spread until corralled by the wind. Signs of burning were less powerful: fine fuels still remained, and the angle of char was even and level. The investigators started putting flags up to mark the outline of where it seemed the fire had been lit.

Some 26,000 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, four metres inside the plantation. There was no sign of an incendiary device – sometimes investigators would find the remnants of DIY contraptions made with mosquito coils or party sparklers attached to weights – 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.

Henry’s job was just beginning. It is estimated that only 1 per cent of bushfire arsonists are ever caught. As he got closer to the site of the first flame, it felt like he moved further away. The sudden chaos of the indicators is why the area of confidence is also called the area of confusion. Here, at the site of the first moments of ignition, the evidence reveals the morphing power of what is to come.

In the next half­-hour, Henry would drive with Xydias a kilometre up Glendonald Road and, in the rubble that had been a house, find the burnt remains of two brothers. For I have eaten ashes like bread, and mingled my drink with weeping. Psalm 102 was something else the Marist Brothers hadn’t managed to teach him. He would organise for a police guard to stay on site until the rest of the specialist forensic team arrived on Monday morning. Right now, although it wouldn’t get dark for another couple of hours, it was too perilous to drive much further into the wreckage. Roads were still lined with burning trees, their branches waiting to fall.

Instead, Henry planned to check in at the region’s police headquarters, 10 minutes away in Morwell, and after that, crash for the night at the local motel. He would live here for the next few months. Little plastic­-wrapped soaps, long­-life milk in the bar fridge, a photo of his new daughter on his phone – the world made miniature, ordered and secure.

A century ago, Henry Lawson wrote that arson expresses a malice “terrifying to those who have seen what it is capable of. You never know when you are safe.”

As the scientists inspected the ground for signs of whatever the arsonist had used to start the fire, Adam Henry stood in the area of confusion and wondered, Why? He’d been trained to think of motivation first – why, then who. So, was this a vendetta? Was it random? Did the arsonist live nearby? Or did someone whom the arsonist was targeting? Was it an act of revenge? Why the plantation? Plenty of environmentalists had protested the slow death of the forest; the privatisation of the Strzelecki Ranges had seen much of what remained of the old­-growth mountain ash and blackwood cleared for monocultures of pine and blue gum. Was it for the thrill, the power? Was it psychosis?

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?

The scientists were not the kind to anthropomorphise. And yet they did. “Flank”, “head”, “back” or “rear”, “fingers of flame”, “tongue”, “tail”: despite themselves they described a beast. The low­-hanging smoke drifted around the burnt trees. A sprite may as well have visited the forest and left one tiny spark, one curling lick of flame that begat this monster, which grew a tongue, a head, flanks and claw­-like fingers, and stretched for mile after mile, taking whatever it wanted.

Who, and why?

This is an edited extract from The Arsonist by Chloe Hooper (Penguin; $34.99), available now.