On 29 August 2016, the Tromp family vanished from their Silvan farm without warning. They left their phones, passports, bank cards, and vehicles behind, and drove north as if escaping an unseen threat. Within days, all five family members were scattered across two states lost, confused, and acting as though danger was closing in, even though none existed.
A Stable Family Begins to Fracture
Mark and Jacoba Tromp lived on a large property in Silvan, on the outer edge of Melbourne. They ran two businesses from the farm a redcurrant operation and an earthmoving company. Both were steady, long-running sources of income. Their three adult children, Riana, 29, Mitchell, 25, and Ella, 22, were closely involved in the family’s day-to-day routines.
The Tromps had no criminal history, no financial problems, and no recorded mental-health issues. Police later confirmed they were not in debt and were not under investigation. To neighbours, the family appeared stable, hardworking, and tightly connected.
But in the weeks leading up to 29 August 2016, things began to shift inside the home. Mark and Jacoba grew anxious. They started to believe someone was watching them. The idea didn’t fade it grew. They feared people were trying to harm the family or take control of their business. These were not passing worries. They were strong, fixed beliefs.
Their behaviour changed with it. Inside the farmhouse, business documents were pulled out and sorted into piles. Financial records were checked over and over. Nothing was stolen. Nothing was missing. Yet it looked like the parents were searching for proof of something they couldn’t name.
Police later said the papers were arranged in a way that suggested a focused, urgent search not normal clutter.
The children noticed the change immediately. Mitchell said he had never seen his parents behave like this. Conversations that once made sense were now driven by suspicion. Routine decisions when to leave the house, who to speak to felt dangerous to them. The fear in the home was constant.
By late August, the belief that someone was after them became overwhelming. Mark insisted the family was in immediate danger. Jacoba supported him. Their shared conviction became the centre of every discussion. The children disagreed but were unsure how to challenge fear that strong.
On the night of 28 August, the parents decided they had to leave the property. Not later right away. They believed staying in Silvan put all five of them at risk.
At dawn on 29 August 2016, the decision became action. The family left without packing clothes or essentials. They walked out without their phones, passports, bank cards, or even the keys to their other cars. The farmhouse door was left unlocked.
They climbed into Ella’s silver Peugeot and drove away from Silvan, convinced an unseen threat was closing in.
The Sudden Flight From Silvan
When the Tromps left Silvan on the morning of 29 August 2016, they left behind almost everything. Phones, wallets, credit cards, passports all were still inside the house. Several cars sat in the driveway with the keys still in the ignition. The farmhouse door wasn’t locked. Nothing about the departure looked planned.
Inside, police later found documents spread across tables and benches. Business papers, financial statements, invoices, handwritten notes sorted into piles but left behind as if the family had been searching through them until the final moment. It looked deliberate, not careless. Something had pushed them to leave in a hurry.
They drove north in Ella’s silver Peugeot. At first, the children assumed they were just going for a short break to calm their parents’ nerves. But not long into the trip, the paranoia intensified. Mark and Jacoba became convinced they were being tracked. When Mitchell’s phone rang, they insisted it had to go. They believed the phone could reveal their location.
Mitchell didn’t argue. He rolled down the window and tossed it out onto the road.
The family kept driving. They didn’t stop for food or rest. They travelled through the day and into the night, covering nearly 800 kilometres. By early morning on 30 August, they reached Bathurst in New South Wales.
The stress of the trip was wearing them down. Mitchell, the only one who still felt grounded, tried to reason with his parents. But their fear was stronger than anything he could say. At Bathurst, he decided he couldn’t continue. Staying with them meant being pulled deeper into the panic.
He left the group and took public transport toward Sydney, then back to Melbourne. He later said he went along only to keep everyone safe, but he had never seen behaviour like this from his parents.
With Mitchell gone, the remaining four Mark, Jacoba, Riana, and Ella continued the journey alone. They turned east toward the Jenolan Caves, still acting as though someone was following them.
The danger they feared wasn’t real. But by this point, the family was reacting to it as if it was.
Breakdown at Jenolan Caves
After leaving Bathurst, the remaining four. Mark, Jacoba, Riana, and Ella drove east toward the Jenolan Caves. The atmosphere in the car was tense. The parents’ paranoia had intensified, and every passing vehicle or unfamiliar sound seemed to confirm their belief that they were being followed.
By the time they reached the caves, the daughters could no longer ignore how unstable the situation had become. Their parents were acting unpredictably. Conversations looped back to the same fears. Nothing they said could calm them down. The sisters began to worry for their own safety.
At Jenolan Caves, the pressure finally broke. Riana and Ella decided they had to get away from the fear, from the confusion, and from their parents’ increasingly irrational behaviour. With no phones and no way to call for help, they acted on instinct. They found a parked vehicle with the keys inside and took it.
They drove south toward Goulburn, a regional city several hours away. During the trip, they tried to make sense of what had happened at home and why their parents were behaving so strangely. The fear that had kept them together was now pulling them apart.
When they reached Goulburn, the two sisters went to police and reported their parents missing. They explained that the family had fled Victoria without warning and that Mark and Jacoba had become paranoid and unpredictable. Officers took their statement and began alerting other jurisdictions.
But even after reaching safety, the sisters’ ordeal wasn’t over. At a petrol station soon after, they separated again. Ella suddenly said she needed to return home to feed her horses. It was a practical thought in the middle of chaos, and she followed it.
She left Riana in Goulburn and began the long journey back to Silvan, eventually reaching the farm later that evening. Police were already inside the house when she arrived.
Riana stayed behind. Alone, frightened, and exhausted, she wandered Goulburn trying to stay out of sight. At some point, she climbed into the back of a ute parked nearby. The driver didn’t notice her until nearly an hour later, when he stopped and found her curled up in the tray.
She couldn’t explain who she was or how she had gotten there. She seemed confused, shocked, and unable to process what was happening.
Paramedics were called, and she was taken to Goulburn Hospital. Doctors said she was deeply disoriented and in no condition to face charges for the stolen vehicle. She was admitted for psychiatric care.
By now, the three siblings were all in different places home, hospital, and in transit and their parents were still somewhere on the road, moving without a plan and guided only by fear.
Parents Split and Disappear Again
While their daughters were reaching Goulburn, Mark and Jacoba continued moving south from the Jenolan Caves. They were still convinced someone was following them. They avoided major roads and made unpredictable turns, trying to stay ahead of an imagined threat.
By Wednesday morning, their route brought them into Wangaratta, nearly 600 kilometres from where the journey began. At some point in or around the town, the couple split up. How it happened remains unclear.
There were no witnesses, no explanation, and no signs of an argument. They were simply no longer together.
Jacoba traveled north an unexpected and unexplained direction. She somehow covered hundreds of kilometres without any record of how she got there. No one saw her hitchhike, board a bus, or enter another vehicle. Yet by Thursday morning, she was found wandering the streets of Yass, a town roughly 350 kilometres away.
Locals noticed she looked confused and distressed. Police were called. When officers arrived, Jacoba seemed disoriented and unable to explain how she had traveled so far on her own. She was taken to a nearby hospital for immediate care. Doctors later transferred her to Goulburn, placing her in the same facility where her daughter Riana was being treated.
Back in Wangaratta, Mark remained on the move. Witnesses saw him driving erratically, tailgating a young couple at dangerously close range. Not long after, he abandoned Ella’s silver Peugeot on a dirt road and fled on foot.
Police later connected this timeline to several small break-ins reported nearby, including a disturbance at a motel. They never confirmed whether Mark was responsible, but the timing raised suspicion.
For several days, Mark stayed out of sight. Police searched bushland, roadsides, and nearby properties. Air support was brought in. The investigation now spanned two states, and the public followed every update, trying to understand how a stable family could unravel so dramatically.
On the sixth day, the search ended. Officers found Mark sitting by the roadside near Wangaratta Airport. He appeared tired but not injured. He did not resist when police approached. He was taken for a mental-health assessment and then released into the care of his brother, who was a police officer.
As he was driven away, photographers captured Mark raising his middle finger a moment that quickly spread across national news and became one of the most recognisable images of the case.
With Mark and Jacoba now located, all five members of the Tromp family had finally been found. But the question remained: what exactly had caused the collapse?
Explanations
With every family member now located, police began examining what had caused the disappearance. They found no sign of an outside threat. No one had been following the Tromps. There were no debts, disputes, or criminal issues. Their businesses were stable. Nothing suggested a danger that would force a family to flee across two states.
Investigators also looked at the possibility of chemical exposure from the farm something that might trigger confusion or hallucinations. Tests later ruled this out. There was no poisoning, no contamination, and no medical evidence supporting that theory.
What remained was a psychological explanation. Mental-health specialists pointed to a rare condition known as folie à plusieurs a shared delusion. It occurs when one person’s strong belief, often fueled by stress or fear, spreads to close family members. In this case, Mark’s belief that the family was in danger appeared to influence the entire household, including Jacoba and the three children. The fear grew quickly, and the group reacted as if the threat was real.
Later interviews supported this view. Riana said the family was “embarrassed” by what happened and never wanted the attention. Mitchell called the experience the most shocking behaviour he had ever seen from his parents.
Ella said she remained confused about the trip but admitted her father had been struggling mentally for some time. She noticed his stress building long before they left Silvan, but she didn’t understand how severe it had become until they were already on the road.
Police chose not to prosecute Riana for the stolen vehicle due to her medical condition at the time. Ella did face a theft charge for the car she and her sister used to escape, but it was later dropped after an agreement with the owner.
Aftermath
In the days after being found, Mark issued a public apology. He said he regretted the distress caused to the community and the resources used during the search. His tone stood in sharp contrast to the chaotic moments that had defined the week-long ordeal.
With time, the family returned home and resumed work on the farm. They kept a low profile and remained under the care of health professionals. Friends and neighbours supported them quietly, helping the family regain a sense of normal life.
For many Australians, the Tromp case became one of the most unusual events in recent memory a story of a stable family that suddenly unraveled, guided not by an external threat, but by fear that spread from one person to everyone around him.
