Well before dark, by Maryrose Cuskelly

On 6 March 2015 at St Ambrose Anglican Church in North Mackay, Queensland, a funeral was held for Marilyn Joy Wallman. The day chosen for the service would have been her fifty-seventh birthday. Some three months earlier, in a televised press conference, Queensland's Assistant Police Commissioner Mike Condon announced that a fragment of skull found in October 1974, two and half years after she went missing, had been confirmed as belonging to the fourteen-year-old schoolgirl. Beside him sat the Wallman family – Marilyn's parents John and Daphne, her brothers Rex and David, and her sister Lenore – heavy with grief, no less leaden for being more than four decades old.

Marilyn, five foot four inches tall and slim with red hair and freckles, left her home on her family's sugarcane farm at Eimeo near Mackay, a little before 7.45am on Tuesday 21 March 1972. As usual, she rode her bicycle down a side road towards the Rural Youth Hall on the Bucasia-Mackay road where she would catch the bus that took her to school in North Mackay. It was sports day and she was wearing her white sports uniform, white socks and sandshoes. Her two younger brothers, ten minutes behind her and on their way to the nearby primary school, came upon her bicycle lying by the track, its front wheel still spinning. It lay in a slight dip about 180 metres from the hall and roughly a kilometre from their home, visible neither from the Wallmans' house, nor from the bus stop. Her school port lay open on the ground beside her bicycle, her belongings strewn about. On either side stretched fields of sugar cane. The start of the harvest was three months away and the cane grew thick and high.

The brothers knew the instant they saw their sister's toppled bike that something was dreadfully wrong. Eleven-year-old David ran home to fetch their mother. His brother Rex, two years younger, remained beside their sister's things. As he waited, he heard a cry coming from the cane. In the days and weeks that followed, despite relentless questioning, despite everything, he never shifted from his story: it was Marilyn's voice he heard; she said that her legs hurt.

For weeks, police and the people of Mackay and the surrounding districts searched for Marilyn. The Daily Mercury, Mackay's newspaper, praised the hundreds of searchers – business men, farmers, labourers, youths with long hair, coloured people – who strode shoulder to shoulder through cane fields, thick clumps of guinea grass and bushland. Others were on horseback, riding motorcycles or in four-wheel-drive vehicles. Yet more combed beaches, dragged waterholes and searched ditches and culverts for miles up and down the Pacific Highway. Unexplained lights were investigated, reports of teenagers in cars treated with suspicion and consideration given to the insights offered by clairvoyants and dowsers.

I was a child when Marilyn Wallman went missing and a skilful eavesdropper. I heard the words pervert and interfered with and I drew my own conclusions.  Little pitchers have big ears, the grown-ups would say to each other when they noticed me lurking. Sometimes, one of the adults would reach out and draw me close, holding me briefly and fiercely, before telling me to scoot.

North Queensland is Australia's gothic heartland, with a reputation for death and missing children. It isn't only the familiar story of violence, dispossession and disease that decimated the Indigenous population in the years after white settlement, or even the practice of blackbirding that saw tens of thousands of South Sea Islanders press-ganged into working in the state's cane fields in the latter decades of the nineteenth century. Tales, true and apocryphal, of murder and misadventure linger in the memory of the people, in the names of landmarks and in the country itself. Into the late seventies, the drive to Mackay from the south of the state remains daunting because of the Horror Stretch, the 300 kilometres or so of isolated highway that runs between Marlborough, just north of Rockhampton, to Sarina, a few kilometres south of Mackay. Cars frequently come to grief on the narrow section of bitumen and the scrubby, sparsely populated landscape through which it runs offers little comfort to nervous travellers.

At the time of Marilyn's disappearance, the people of north Queensland are still living with the unsettling knowledge that whoever killed five-year-old Susan and seven-year-old Judith Mackay (their surname the same spelling as the township) less than two and a half years earlier is still at large.

In August 1970, and some 389 kilometres further north along the coast from Mackay, the sisters went missing from a school bus stop a short distance from their home in Townsville. Their bodies were found two days later in a dry creek bed. They had been stabbed, raped and strangled. Their clothes, neatly folded, lay beside them in terrible counterpoint to their ravaged bodies.

Mackay and the centres further north are sugar towns. When the cane burns scraps of ash drift in the gathering dusk and pirouette down to float on the surface of backyard swimming pools. At harvest time, the cloying smell of molasses hangs in the air. Water is never far away, and where it lies, vegetation grows rainforest thick. During the wet season, the air is syrupy with humidity. The day after the discovery of the sisters' bodies, a journalist from Brisbane's Courier Mail asked, Could the North Queensland tropic climate be linked [to the crime]? The sudden return of early spring after a short winter?

Only days before Marilyn Wallman disappears in March 1972, newspaper headlines across the state announce concerns for yet another lost child north of the Tropic of Capricorn and many miles to the west. Two-year-old Shay Maree Kitchin has been missing from her Mount Isa home since the previous Sunday evening. Shay Maree, the police are told, disappeared on her way to the shop to buy lollies. In a few days time, Shay Maree's body will be found in a paddock and her mother's de facto will be charged with her murder.

A week or so after Marilyn goes missing, Queensland Police Minister Max Hodges urges parents to warn children about the danger posed by strangers. He issues a list of six cautions he recommends parents impress upon their offspring. The list becomes an article of faith for my siblings and me:

Never talk to strangers.

Never accept offers of lollies or presents.

Never accept offers of a ride in a strange car.

If approached by a stranger, tell a policeman or run to the nearest house and tell the occupant.

Always go straight to school and come straight home.

Be home from parks and playgrounds well before dark.

The early 1970s are uncertain times. Several weeks after Marilyn Wallman's disappearance, the Labor MP for Mackay Ed Casey warns that the morals of Australian society are beginning to degenerate to the level of communist philosophy. He cites sexual freedom among students, the illegitimacy birth rate, drug use, student demonstrators and hippies – bludgers of the first order – as examples of this decline in decency.

My two older sisters have left home and are living in a sprawling share house in Brisbane. They and their friends are among the bludgers of the first order protesting against the 1971 South African rugby tour of Australia. The police, with Premier Joh Bjelke-Petersen's tacit approval, respond with violence against the demonstrators. There is blood and broken bones. My father names our new dog Springbok to provoke his daughters.

My sisters and their friends are enthusiastic about the prospect of Gough Whitlam's election and his promise to end conscription. In the months before Marilyn's disappearance, they are among the hundreds who once again clash with police in demonstrations supporting the anti-Vietnam War moratorium. They wear T-shirts emblazoned with ‘It's Time’ and treat my mother's fears, that Whitlam's embracing of 'Red' China means he will nationalise the farms, with condescension. For the first time I see the jarring cover of The Female Eunuch when we visit my sisters in Brisbane. The abstract, yet graphic, representation of a woman's headless and limbless torso is both menacing and titillating. The little red school book, written by Danish schoolteachers Søren Hansen and Jesper Jensen doesn't make it to our little country school, but there is fuss and bother about its frank discussion of sex and drugs and its encouragement of school students to interrogate authority.

The rule is that the eldest is in charge. On our way to and from school, my oldest brother, at eleven years old, is a natural and enthusiastic tyrant. We must walk in single file from oldest to youngest and I trail behind my three brothers at the end of the line. On our way home, our leader often spurns the most direct route along the road and opts for a more challenging trudge up hills, through barbed wire fences and across paddocks studded with toe-stubbing rocks, low-growing cactus and bullhead thorns. If he chooses to push through a thicket of acrid-smelling lantana with its trailing barbed branches that tear at our skin or to scramble down the wall of a steep gully and scale the other side, so must we. By the time we drop our school ports on the kitchen floor, I am often scratched and weeping.

There is another rule: under no circumstances must we arrive home later than 4 o'clock. This one works against our leader and, consequently, the rest of us in his merry band. My brothers are indignant that my tear-streaked face is enough to spare me from the physical punishment my mother reserves for flouting this rule – a switch of the iron's electrical cord against our bare legs. They accuse me of only starting to cry once I see the cord in my mother's hand.

Now, as an adult, I hold no rancour about the ironing cord. I know my mother's disquiet. It's familiar to every parent who has contemplated the loss of a child; the heart pauses as if clutched by a cold hand and then is released to gallop in an erratic rhythm driven by dread.

Perhaps in response to the Marilyn's disappearance and the failure to find her abductor, a roster to drop off and pick up children from school is organised among the farmers who live on our side of the local hamlet. We pile into cars, cram into the boots of station wagons or vie for the privilege of riding in the back of the ute with the big kids. Toddlers perch on older siblings' knees on the front bench seat, while six kids sit one-back-one-forward along the seat behind, unsecured by seatbelts. We are in far greater danger of injury from being flung off the tray of the ute as we round a corner, or being crushed to death in a collision with the milk truck on the narrow roads, than being abducted by a stranger as we walk to school.

In October 1974, a young railway worker takes a walk beside a creek near Mirani, about 40 kilometres from where Marilyn Wallman was last seen. Looking to cut palm leaves to shade his mother's orchids, he comes upon a piece of bone, immediately identifiable as part of a human skull. He assumes the thing is ancient and treats it like a curio, showing his friends and handling it freely. Three weeks later the local copper gets wind of the find and directs the young man to hand in the fragment to the Mackay police.

It will take decades for the technology to develop that can isolate a sequence of mitochondrial DNA linking the fragment of bone to Marilyn Wallman's mother. Several more years will elapse before further tests can provide enough weight to the link that police are able to present a case to the Coroner allowing him to rule that the remains are indeed of the schoolgirl.

In the intervening years, the Wallman family strive to keep Marilyn's case alive in the public mind. In 2002, Arthur Stanley Brown, the man charged with the murders of Susan and Judith Mackay, but deemed too senile to be tried, dies. There are some who suspect he may have been involved in the disappearance of other children, including Marilyn Wallman. In 2013, due largely to her family's urging, a $250,000 reward is offered for information leading to the apprehension of Marilyn's killer. The following year, when police excavate the backyard of a North Mackay house, hopes are high for a breakthrough. It comes to nothing. There is another flurry of expectation in March 2016, when soil samples are taken from the place the skull fragment was found and the surrounding area comprehensively mapped. Any findings are yet to be announced. And still the Wallman family wait and hope for answers to their questions about what happened to Marilyn.

It is my firstborn son's fourth birthday and I take him and his 20-month-old brother to the Melbourne zoo. I am amused but discomforted when a small female mandrill approaches and displays her brightly coloured rear end to my son as he jumps up and down in front of the glass barrier. He is wild with excitement and runs ahead of me as I push his brother's pram up the incline of the raised walkway that takes visitors treetop height past the monkey enclosures. Within seconds he has slipped into a large group of school children of a similar size to him and wearing almost identical hats, shorts and T-shirts.

I don't panic. I will catch up with him soon enough. He will be watching the black-capped capuchin babies taunt their elders or the spider monkeys swinging through the canopy using their prehensile tails and long, elegant fingers. But he is at neither of these enclosures. I pick up pace, scanning each small face beneath every oversized sunhat. The bulk of the pram and the numbers of children on the ramp hamper my progress. I reach the end of the walkway and he is nowhere to be seen.

I am already grappling to keep at bay the thought that I may never see my son again. My dread, sudden and certain, is fuelled by images snagged on the ragged edges of my subconscious since childhood: a toppled bicycle, one wheel slowly turning; a young boy crouched beside his sister's belongings; a cry, thin and muffled rising from the cane. When I find the building where lost children are cared for, my son is there. He scolds me for allowing us to get separated. Then he lets me hold him, briefly and fiercely.