THE last time her family see her, she turns on the doorstep and says "Bye, Mum, see you later." It is about 8.20am on a Thursday, six months ago tomorrow.

She crosses the street to the footpath and heads towards high school, a few minutes' walk.

Two doors down, a neighbour glances through his living room window and glimpses her: a 13-year-old girl in a blue and white uniform and blue rain jacket, carrying a dark backpack.

She moves from right to left across his vision - for about three seconds, he later calculates.

Then she vanishes.

Whoever sees her next, you'd think, is the only person who knows what happened to her, and why. The only one who knows if she is alive or dead.

Her family call her Bung, a short name standing in for the one on her passport, Siriyakorn Siriboon. She is a good girl: diligent, punctual, polite, never wags school.

People trust her, so when she doesn't turn up in her year 7 class that June morning, everyone assumes she has stayed home because of illness. It's the first week of winter, what teachers call "flu season", when kids wake up feeling awful and can hardly drag themselves out of bed.

If Bung were a troubled child, a repeat truant, teachers might suspect she is off on an escapade of her own. But she is none of those things, so no one worries until later.

At 3.30pm her mother, Vanidda Pattison, realises her daughter isn't home at the usual time. She calls her name from the kitchen, wonders why there's no answer.

About 4pm, the telephone rings. Bung's stepfather, Fred Pattison, answers. It's Dyamai, Bung's school friend. She asks to talk to Bung about what to wear to football practice next day.

It's the first Fred has heard that Bung wants to play football, as well as training for athletics and the school's rock eisteddfod.

"Why didn't you talk to her at school?" he asks, puzzled.

The girl hesitates. Bung wasn't at school, she says.

That's how the torment starts. First they go to the school, Boronia Heights Secondary College. The principal, Kate Harnetty, is still in her office, working late.

Harnetty has seen Fred Pattison at school functions and noticed he is calm and polite, and shows more interest in his stepdaughter's progress and behaviour - both good - than many fathers do.

She doesn't know his wife as well because Vanidda, only four years out of Thailand, isn't confident speaking English with strangers.

The Pattisons try not to panic. They look in the school library to make sure Bung isn't there. The principal checks the year 7 roll then finds a teacher who confirms Bung hasn't been in class.

That's when Kate Harnetty knows they have reason to worry. Bung doesn't "fit the mould" of kids who play truant or run away from home, as she later recalls. "She's just a sweet little girl. It was out of character."

She urges them to go straight to the police.

Minutes later, Fred Pattison walks into the police station in Dorset Rd. On the wall in the waiting area is a poster that says: When someone goes missing a day spent waiting is a day lost.

It's true enough but truth does not always equal reality in police work. The reality is that more than 35,000 people go missing in Australia every year, and more than half of them are under 18. The overwhelming majority turn up safely in hours, days or weeks.

But it's almost impossible to guess which tiny proportion of missing person reports could turn into something more sinister.

The policewoman who appears from behind the one-way mirror is polite and sympathetic but has no reason to think the report is different from the many that come to nothing.

In any case, the search has to start close to home, with friends and family that parents can reach quicker than the police can.

Fred has been up all day doing chores after night shift as a fitter in a Scoresby confectionery factory. Normally, he would take a nap and go to work. Instead, he calls his boss to say he won't be in.

In fact, it turns out he will not be back for a month.

Fred and Vanidda stay up all night. First, they visit Bung's friend Dyamai to get the names and telephone numbers of Bung's other friends. They call or visit each one.

Every blank they draw deepens their fear - and sends widening ripples of alarm. Late-night phone calls between other parents, school friends and teachers draw more people into the puzzle but no one knows the answer.

By 8am the Pattisons are back at the school, distraught, waiting to talk to the one classmate they missed overnight, but the girl knows nothing.

Kate Harnetty sees the overnight change in the couple: the hollow eyes and anguished faces. She urges them to go back to the police.

As soon as they leave, she calls the station to make sure they are taken seriously. With Fred Pattison's full-arm tattoo, cropped hair and tiny plait, she knows he looks "a bit like a merchant seaman" and fears he and Vanidda might be dismissed as trouble-prone time wasters.

As Pattison says later, he "hassles the police a bit" that morning. At that point it's still not unreasonable to suspect that Bung has run off with someone, and is now nervous about coming home.

Her parents are desperate to believe this, but too fearful to wait and do nothing. They make up simple posters: a snapshot of a smiling Bung in school uniform.

One of Fred's workmates helps put up the posters all over the district, first on power poles along the route Bung walked to school, then further away, in shops, bus stops and railway stations.

About 2pm, Knox Leader trainee reporter Erin Michael is buying a coffee in the Boronia Mall when she sees Fred Pattison taping up a poster. She introduces herself.

"He seemed quite vague and shocked," she would recall. "He came over to the office. He was pretty emotional." Half an hour later she puts the story online. That night, the Herald Sun picks it up. So as day two ends, the mystery is public - but deepening.

With every hour, the Pattisons grow more fearful. They put up posters all weekend.

By Monday, June 6, Knox detectives are on the case. A police spokesman concedes they have not "ruled out abduction". It's the first time the spectre of kidnapping is officially raised.

Inevitably, there are false leads and false hopes. On Tuesday, June 7, the trail is muddied when a schoolboy reports he saw Bung in Chandler Rd after school on the day she disappeared.

It turns out to be another Asian girl in school uniform. A security guard thinks he saw Bung at the railway station. He is wrong, too.

On Thursday, June 9, police set up an "information caravan" along the route Bung usually walked to school. People trickle in to talk. There is speculation but not much information. Nothing leads anywhere.

Detectives need a door to knock on, a car to trace. At the end of the first week they have neither. Twenty-five weeks later, they still haven't.

IT is just after 8.20am on a recent Thursday, much the same as the morning Bung walked out the door of the little house halfway along Elsie St. This is where suburbia meets the bush.

Cockatoos, magpies, crows and parrots squabble in the trees that fill the big post-war house blocks next to the Dandenongs. It's more Neighbours territory than the place for a horror story.

In the cream brick veneer at No.55, Vanidda Pattison is packing. Months of waiting for the news she dreads have taken a toll, though she tries to mask unspeakable fears with animated conversation, smiles and laughs.

She stays busy, but when she stops for a photographer to take a picture, the camera does not lie. Frozen in every frame, her eyes are full of pain.

Reliving the moment she realised Bung hadn't got to school that day, she holds her face in her hands. A policewoman, herself a mother, puts her arm around Vanidda as she talks of the last time she saw her girl.

When Fred got home from nightshift about 7.30am that Thursday, Vanidda was cooking chicken curry soup and rice for breakfast. "Bung had that breakfast," explains Vanidda. "Then she took some for lunch. The canteen is not nice for her."

They almost always refer to her in the present tense and cling to the belief she is alive, somewhere, somehow. It's a way to cope with a loss beyond words.

Vanidda is small, wiry from a lifetime's hard work and the simple diet she has followed most of her 42 years. She grew up in Ubon Ratchathani province in northeast Thailand. Her first marriage ended when her two girls were small, and her parents helped raise them while she worked. Now she is going home to see her mother and father.

She and Fred own a house in Thailand and were intending to move there after Bung finished school. Now everything is on hold.

Stacked on the couch are gifts for her family and the Buddhist temple in their home town. Early on the day Bung went missing, Vanidda and Fred had gone to the Bunnings store in Bayswater to buy roofing screws and sensor lights to donate to the temple. They believe in karma. Faith helps them get through each cruel day.

Vanidda met Fred in Melbourne when she was on holiday seven years ago. He spoke passable Thai, having spent a year there on long-service leave and studying the language at home.

His interest in Buddhism grew from his dedication to sado karate, which he took up at 15 and has practised ever since.

He admires the Thai work ethic and family values. Vanidda - he calls her "Nid" for short - "is a hard worker", he says. "It's a cultural thing. A good thing."

Together they have transformed the garden of the house they bought from an old couple four years ago. They also pounded the streets "letter boxing" retail catalogues together to earn extra money and keep fit.

Pattison understands self-reliance and hard work. He grew up in a battling family of nine around Queenscliff and Portarlington, then moved to Melbourne as an apprentice fitter at Carlton United Breweries, aged 17.

He still barracks for Geelong; Cats premiership posters are taped next to the front door but he's not had much appetite for footy since June 2.

It's the same with the fishing boat in the yard. He bought it last year but has never used it. He is holding down his job, thanks to an understanding employer, but the rest of his time is devoted to holding the family together, including Bung's big sister, Siriporn, now 20, a student at Swinburne.

Pattison is calm and self-possessed. He doesn't swear or bluster to mask his anguish, and he looks people in the eye. It's clear why investigators soon decided he had nothing to do with his step-daughter's disappearance.

He bears no grudges that detectives questioned them so closely. That is how it goes when someone vanishes. Family members and friends have to be cleared first. Then neighbours and workmates, outwards in widening circles. But if that doesn't work, then what? That's the question the Puma Taskforce faces.

'What we've got," says an exasperated Detective Superintendent Brett Guerin, "is a big bag of fresh air."

Police are rarely so frank in public. But the dozen investigators recruited for the taskforce in October know what their boss means. This could be the toughest assignment of their careers.

Not only do they have no leads, they are starting behind scratch because of a false one.

On June 29, almost four weeks after Bung disappeared, a Boronia primary pupil was late for school. Asked why, she lied that a grey-haired man wearing a surgical mask had tried to force her into a green Holden station wagon.

Trapped in the lie, the girl did not confess for more than a week. The nonexistent kidnapper and his green Holden had been widely publicised because the supposed "victim" was also an Asian girl

and the scene was near where Bung lived.

The hoax overshadowed a genuine abduction attempt a week earlier. On June 21, a middle-aged man with greying hair and decayed teeth had tried to drag a 16-year-old schoolgirl into a blue sedan in Bedford Rd, Ringwood East.

Investigators don't want to pin their hopes on the Ringwood incident but they can't ignore the fact it happened only 10 minutes from Elsie St, less than three weeks after Bung disappeared.

When the man with the bad teeth and blue car is found, he will have the taskforce's undivided attention. Meanwhile, no one wants to say they are most likely looking for a killer. Even though the homicide squad is running the taskforce, and no matter how likely abduction and murder might seem, investigators must keep an open mind.

Without leads, they have to consider all possibilities - even the faint one that Bung left voluntarily, which would mean no crime was committed. It's true some teenagers stage their disappearance but they almost always have reasons to leave home and not return. The investigators are sure none of those usual sordid reasons applies.

Bung was happy at home and school. Her behaviour was good, her attitude consistent and did not change in the days or weeks before she disappeared.

One by one, the taskforce has crossed off theories.

Bung had Facebook friends, just as several million others do. Police have combed the family's computers but found nothing to show she struck up contact with anyone outside her own group.

She left her mobile phone home the day she disappeared but investigators soon worked out that was not unusual.

She had wanted to go to school earlier than usual one day, but police found she had wanted to meet her friend Dyamai, not anyone suspicious.

They are left with a likely scenario that she was lured or forced into a car without being seen. If that did happen, no one wants to speculate on what happened next. But murder isn't an automatic assumption. There have been well publicised cases overseas of girls being abducted and imprisoned, some for years. A copycat crime can't be ruled out.

Neither can police rule out the possibility Bung was abducted by human traffickers to use or sell into what police call "sexual servitude". They checked eastern suburbs brothels after a tip-off that a young Asian girl had been seen in one, and would do the same again. Thai nationals have been involved in sexual slavery scandals in Australia and a Thai speaker might have been able to lure Bung into a car.

These are the bleak possibilities that desperate parents cling to: that a sexual psychopath or a human trafficker has taken their child and kept her alive.

The Puma Taskforce has set up in a big unused room at Glen Waverley police station. With its whiteboards, computers and telephones, it could be any tired suburban office but for one thing: the work here is deadly serious.

The office is within easy reach of Boronia, but far enough away to suit anyone who wants to talk to police without being seen by neighbours or relatives. The success or failure of a long investigation could rest on such subtleties.

The investigators have to look for clues they are not sure exist. It is like sifting tonnes of beach sand in the hope of finding a tiny mystery object that might have been lost somewhere else, or not at all. Persistence and concentration is everything.

First, they have to interview, or re-interview, about 400 householders who live along the streets between the Pattisons' house and the school, then work outwards. They have to trace every conceivable visitor - tradesmen, salesmen, delivery drivers, postmen - who might have been in the district in June.

They have to find every registered sex offender and test his alibi for that day. Next, they have to identify suspects who might never have come under notice before.

To do this they need help from people who can suggest anyone that might have had an excuse or an opportunity to be near Boronia on June 2.

They need people to confide a suspicion or a secret about a relative, neighbour or workmate. The police would never put it so bluntly but their message could be reduced to this: The vanished girl is someone's sister, someone's daughter - she could have been yours. And whoever took her is somebody's brother, someone's son. Someone knows him.

It takes less than five minutes to walk to the eastern end of Elsie St from the Pattisons' house. About the same to cross Albert St and walk up Harcourt St to the high school's back gate.

It looks so normal to an outsider but life has changed here. Children who used to walk to and from school themselves now go in pairs or groups. Parents eye slow-moving cars suspiciously. Many more now juggle their lives to drive children to and from school.

Bob and Nancy Downward have lived at 73 Elsie St since 1956. They used to see Bung walk past most days, head down.

Since June, the Downwards pick up their 11-year-old grand-daughter from school every day and look after her until her mother finishes work. "Once, you knew everybody," says Bob, a retired brickie. "Now there's some weird people out there."

Down the road at No.55, Fred Pattison runs through the options they allow themselves to think about.

"Maybe someone befriended her over time," he says quietly. "Maybe someone who spoke Thai. Or maybe someone just grabbed her and put her in a car. She was such a lovable kid. Maybe they took her to raise as their own. All the monks and mediums we speak to tell us she's alive and wants to come home. We can't and we don't think anything else but that. We still think she's coming home."

Every school day, Bung walked past the pole on the corner of Harcourt and Albert streets. It has dozens of rusting staples in it from notices put up over the years - for lost pets, garage sales and the like.

Now there is only one poster on the pole, one the Pattisons put up that first fearful day.

Bung's photograph has faded, and wind, rain and insects have invaded the clear plastic cover. The paper is frayed so the telephone numbers are no longer readable. There is something pathetic about it that brings a lump to a stranger's throat.

Opposite the Pattisons' house lives an Elsie St lifer that everyone calls Trudy. Like Bung, she was a migrant girl. She arrived from Holland in the 1950s and has lived here ever since.

Trudy loved the way her new neighbours Fred and Vanidda turned the tired block across the road into a pretty garden, with a new fence, gurgling pond and flower beds. Now she finds it heartbreaking.

The old woman looks across the street at the Pattisons' car parked in the drive, two "Missing" posters still taped to the back window. They, too, are starting to fade. "I pray for her every night," she says, and her eyes glisten with tears.

Spread the word on Twitter and help find Bung by using the hashtag #findbung

It is six months tomorrow since Bung disappeared as she walked to school in Boronia.

She is believed to have been abducted.

The head of the homicide squad, Inspector John Potter, said there were still no suspects in the baffling case.

Bung, 13, was last seen in Elsie St, Boronia, on her way to Boronia Heights College on June 2, wearing a blue and white school uniform and a blue school raincoat.

Detectives have examined all CCTV footage in the area and have questioned and investigated the alibis of almost 100 registered sex offenders in the Knox area.

They are still checking out the alibis of a few of those people.

Anyone with any information should call Crime Stoppers on 1800 333 000.

Spread the word on Twitter and help find Bung by using the hashtag #findbung