Police are ramping up the search for missing Australians and have released their case files hoping details of the disappearances could unlock crucial evidence.
While all missing persons cases are tragic, some are particularly incomprehensible and police have hoping a member of the public might hold the key.
Aboriginal and Torres Strait Islander readers should be advised this article contains images of Indigenous people who may have died.
Megan Mulquiney, ACT
Canberra's police thought they knew who was responsible for the disappearance for 17-year-old Megan Mulquiney, who was last seen leaving work in 1984.
But police reopened the case in 2018 and have been unable to link serial rapist Paul Vincent Phillips to Ms Mulquiney's disappearance.
Police are now looking for leads elsewhere.
Ms Mulquiney finished her Saturday shift at Big W in Woden Plaza at around 12.05pm on July 28, 1984 and left the mall to catch a bus home.
Witnesses saw her at the plaza exit heading to the bus interchange at 12.15pm but she never made her bus.
Her mother Dorothy Mulquiney called police that afternoon but her daughter hasn't been seen since.
Ms Mulquiney was born in 1966 and would be 56-years-old.
Revelle Balmain, NSW
Police were anonymously sent a photo of a man sent to them who could provide the key to finding out what happened to Sydney woman Revelle Balmain, who disappeared 29 years ago.
The NSW Government announced a $1 million reward as part of an appeal for information that may help police find out what happened to her.
Ms Balmain was 22 when she was last seen in the Kingsford area in Sydney's east in the evening on November 5, 1994. She would now be 51-years-old.
She was near Kingsford's Red Tomato Inn with a man on the night she disappeared.
Her make-up bag, keys and a shoe were later found scattered in the same suburb near Ainslie Street.
The model and dancer was reportedly preparing for a six month dance contract in Japan and was due to meet her mother in Newcastle on November 6, 1994, but never arrived.
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Ms Balmain was reported missing but no one has been charged over her disappearance.
A coronial inquest in 1999 found she had died at the hands of a person or persons unknown and the matter was referred to the NSW Police Unsolved Homicide Unit for future investigation.
Last year, a formal review of the cold case began.
Police released an image of a man they wish to identify, who may have information about Ms Balmain's last known movements.
Strike Force Aramac lead investigator Detective Chief Inspector Stuart Bell said the image was sent to investigators anonymously after the reward was announced.
"It is believed that this image was taken some time in the mid-2000s, but that the individual depicted may have information that would help us progress our investigation," Detective Chief Inspector Bell said.
"As always, we continue to encourage anyone in the public that may have information about Revelle's disappearance to come forward and speak with police, so that we may finally provide answers to her family."
Daniel Sheppard, SA
Daniel Sheppard was 19-years-old when he went to a New Year's Eve party with his brother and friends at Lennie's Tavern in Glenelg, a suburb of Adelaide in 1994.
After celebrating he caught a tram into the city to continue partying on Hindley Street.
Mr Sheppard was then seen at the Adelaide Railway Station where he boarded the 4.13am train home to Outer Harbor in the early hours of the new year.
He saw three girls from school among the 30 other commuters on the train.
On the train he told two of the girls that he was "partied out" and was "going home to crash".
He was described as being moderately intoxicated but still in control of his faculties, wearing blue jeans and a maroon denim shirt.
Mr Sheppard got off the train at the Port Adelaide Train Station at 4.35am and was seen on the southern pedestrian ramp going towards Baynes Place on his 10 minute walk home.
He hasn't been seen since.
Police suspect he was murdered and in 2005 a coroner found he was dead after all attempts to find him had failed.
He would be 48-years-old.
There is a $200,000 reward for information that leads to a conviction in this case or the recovery of the victim's remains.
Rebecca Hayward, NT
Rebecca Hayward flew from Perth to Alice Springs on New Year's Day in 2017 to visit her family.
She left the family's house at around 8pm that evening to go for a walk, which wasn't out of the ordinary for a woman described as a "compulsive walker".
But she didn't return home and last seen by two doctors driving on the Stuart Highway around 15 kilometres north of Alice Springs at around 8.30am on January 2.
They offered water and a ride. She took the refreshment but declined the lift.
Ms Hayward is Indigenous with an olive complexion, 173 centimetres tall, medium build with long dark straight hair and brown eyes. She would be 40-years-old.
She was last seen wearing blue denim shorts rolled up to the knees with a green T-shirt and thongs.
Police hold grave concerns for her welfare.
Jake Lyons, VIC
Jake Lyons was last seen leaving his Dandenong North home on August 25, 2014 after dismantling his phone and computer.
His father Rick Lyons farewelled the 20-year-old in the morning but when he returned home from work between 5pm to 6pm the house was unlocked and the gas stove was turned on.
Police believe the younger Mr Lyons went to Springvale during the day to get snacks, drinks and withdraw $50 from a supermarket.
His 2006 Holden Astra sedan was found around seven kilometres north of his home at Warner Reserve in Springvale on August 31, 2014. The keys were underneath the car and the doors were locked.
Since then he hasn't made contact with friends or family, used social media or accessed his bank account.
Police hold grave concerns for his welfare. He would be 29-years-old.
With Australian Associated Press