Stephen Grimmer often wonders what his sister would look like today. He pictures the shape of her face, the length of her hair. He imagines how she might sound.
Mr Grimmer, now 50, was only five when Cheryl vanished from Fairy Meadow Beach on a hot January day in 1970.
The three-year-old's disappearance sparked a massive manhunt and so began one of the Illawarra's most perplexing mysteries.
"I think about it a lot, every day," Mr Grimmer said this week.
"When all these pictures are in the paper again, the profiles of what she might look like, you can't help it," he said.
"I reckon my little fella, he'd resemble her ... when you look at the facial features of when they were both three years old, it's strange really."
Mr Grimmer's dad, Vince, died never knowing the fate of his daughter.
His mum, Carole, is ill with emphysema, but she has not given up hope her daughter is alive.
Mr Grimmer, of Mount St Thomas, wants closure for his family - answers so they can move on from this baffling cold case that stopped the nation and robbed the Illawarra of its innocence.
Brin Grenyer, professor of psychology at the University of Wollongong, said living in limbo was torture for those left behind.
"When a young person is robbed or taken from the family, that leaves a lot of heartache. It tugs us in ways stronger than possibly can be put into words," Dr Grenyer, a practising clinical psychologist said.
"It plays on our minds, in our dreams, our thoughts, and we always want closure on things. We want to know in our own minds that we can bury a person and recognise that they are where we know they are; that they are safe from harm.
"When a person disappears and we don't have that, it's almost like torture. There's the possibility in our minds that we can one day meet them again, that they would still be alive ... maybe they are out there somewhere.
"The critical issue is unresolved grief," Dr Grenyer said. "It's the heartache of the person being lost and an inability to be able to resolve that and settle our minds."
It was January 12, 1970, when the Grimmers' world was turned upside down.
The wind turned bitterly cold about 1.30pm. Carole Grimmer sent her children to shower at the nearby change sheds.
After about 10 minutes, Stephen and Ricky, 7, returned to tell her that Cheryl, who was wearing her royal blue one-piece swimming costume, was still in the men's change rooms.
Mrs Grimmer went to fetch her but Cheryl was nowhere to be found.
So began the frantic search.
Cheryl's dad, a sapper in the army who commuted to Perth, arrived home to join the hunt and was met by the sight of 500 people combing land from Towradgi Beach to Wollongong Harbour.
Detectives made no secret they feared a sexual predator had acted on impulse and snatched the little girl.
Then came a heartless prankster who sent a ransom note demanding $10,000.
Police set up a rendezvous and officers, disguised as council workers, monitored the pick-up point in Bulli.
But nothing - no Cheryl, no kidnapper, just more anguish for the family.
It took 40 years for a coroner to rule Cheryl was dead, but the cause of death remained undetermined.
Coroner Sharon Freund recommended the case be referred to the unsolved homicide squad and sympathised with Mrs Grimmer, noting she had lived "every person's worst nightmare".
The 2011 inquest heard Cheryl was likely abducted from outside the change shed. Witnesses reported seeing a man pick up a child, wrap her in a towel and flee.
Another witness saw a man in the car park holding a fair-haired child before driving off in a white sedan.
Three suspects were never formally eliminated from the investigation. One died in 1995; the other two were never relocated after being interviewed in the 1970s.
A year after the coroner's finding, Stephen Grimmer, who prefers to stay out of the media spotlight, agreed to brave the cameras to appeal for help in solving the mystery.
The NSW government offered $100,000 worth of incentive.
"But since then there's been not a thing," Mr Grimmer said yesterday.
"It's been rough, going through all that, the inquest, where stuff came out that we never knew about. To hear all this stuff, stories, theories about what happened, it's pretty rough. You always wonder."
Which begs the question, how do people move on with their lives after such a traumatic experience?
"Some can can get depressed; it can affect their mental health and who they are, especially when it's a prominent case that gets a lot of media, " Dr Grenyer said.
"Questions like 'who did it' and 'who is responsible' can again really make it difficult to settle these kinds of issues in the person's mind.
"People respond in different ways: some will live with grief; some will be able to take some meaning out of it and rebuild their lives."
Dr Grenyer said sharing their feelings could help.
"It's quite a personal experience - I understand why people would find it difficult and not know how to manage.
"If it's unresolved it's difficult. Clearly family itself needs to deal with it - the last thing you want is a family being split apart - but everyone has to deal with it in their own way and respect that people will have different responses," he said.
"It's always a good idea to talk to somebody about it. If you don't have an opportunity, it can really eat away at you.
"No-one can take the feelings away, but if you share them, it can really help."