Kathryn Gray was eight years old when she last saw her mum and, while the memories have begun to fade, the pain of not knowing what happened to her remains.
"We were her world … it was out of character for my mum to leave," Ms Gray said.
"She wouldn't have walked out on us for sure, I know that in my heart."
"She would have never left me and my brother.
On October 23, 1978, 30-year-old Darlene Avis Geertsema was seen leaving her family home on Best Street in Devonport on the state's north-west coast.
Two days after the mother of six disappeared, her red Holden Sunbird car was found locked and abandoned in a car park on Victoria Parade, near the Devonport oval.
At the time, an investigation into Ms Geertsema's disappearance was undertaken, but police failed to locate the missing woman.
Officers were unable to determine a motive for her departure and her body has never been found.
There have been no confirmed sightings of Ms Geertsema since the night she vanished and police are now offering a $500,000 reward to anyone with credible information that can help investigators uncover the truth about what happened.
Detective Sergeant Felicity Boyd said the reward could be life-changing money for someone.
"Someone out there knows exactly what happened to Darlene that night," Sergeant Boyd said.
"Whilst we have canvassed alternate explanations for her disappearance, we have not been able to find Darlene and we need help from the public to uncover the truth and bring her home.
For the past 43 years, Ms Gray has celebrated birthdays, a wedding and the birth of her children without her mother by her side.
She remembers her mum as being a caring, loving person who adored animals.
"You have the perfect life and then it's gone.
"I know it's 43 years ago, but we're begging anyone with information to come forward.
"You might think it's trivial but, if anyone can remember anything, please come forward and help us to get closure."
'More than likely deceased'
Sergeant Boyd said a review in to the circumstances surrounding Ms Geertsema's disappearance began in July 2013.
She said the disappearance would remain under investigation until Ms Geertsema's body was found or the person or people responsible for her disappearance were brought to justice.
"We have explored several scenarios to explain Darlene's disappearance and whilst we maintain an open mind into the circumstances, we do not believe Darlene left the family home voluntarily," Sergeant Boyd said.
"She would have never, ever intentionally left her children behind and would have never, ever stopped writing to her family.
In December, a coronial inquest will examine how the mother disappeared and consider whether she met with foul play.
Last month, a coroner's court heard that Ms Geertsema's partner, John Shepherd, was considered a person of interest in her disappearance, but no charges have been laid.
Mr Shepherd, who now lives at Westbury, first met Ms Geertsema in 1971 and the pair started dating.
The court was told Ms Geertsema was also having a relationship with a man called Micky Rowe, who lived in Westbury, and whom she intended to marry.
It is alleged that Mr Shepherd told police that Ms Geertsema was in "a very distressed state" before she went missing and that she'd told him that she was pregnant and had cancer.
However, the counsel assisting the coroner said the missing woman had visited a GP on the morning of her disappearance, and the doctor had reported she was "in good spirits, was not pregnant and did not have cancer".
The inquest into Ms Geertsema's disappearance has been set for December 13, 14 and 15 and will be heard in Launceston.
