Australian news report detailing the death of child killer Derek Percy. Video/Channel 7
When suspected serial child killer Derek Percy died in 2013, Karen Stilwell wept.
With his last breath, Percy had taken a secret to the grave. Where had he hidden the body of her seven-year-old sister Linda, 45 years ago?
For days, Victoria Police Detective Senior Sergeant Wayne Newman and Deputy State Coroner Iain West had sat patiently at Percy's side in hospital, waiting for a deathbed confession that would never come, reports news.com.au.
"At one stage they were talking about sending mum in to talk to him but decided not to because of her age and she's not a confident person," Karen recalled. "She was scared stiff.
"I cried when he died because I was so angry that we were never able to get the truth out of him. All we ever wanted was to put her remains to rest but he wasn't going to give us that.
"He had the control until the end. He knew what he had done to Linda and other children but if he admitted to (killing) them he would have lost that control."
Yesterday marked the 50th anniversary of Linda's abduction and presumed murder at the hands of Percy, a sadistic predator linked to a string of high profile child murders and disappearances in three Australian states.
In 1970, the formal naval seaman was jailed indefinitely for the torture and murder of 12-year-old Yvonne Tuohy, who was snatched from Victoria's Westernport Bay in July, 1969 — 11 months after Linda vanished.
For Karen Stilwell and her brother Gary, much of the past half century has been spent replaying their final moments with their sister in their heads, and struggling to survive the misplaced but all-consuming guilt they feel over her fate.
Karen Stilwell, now 61, was 11 years old when her sister Linda was snatched and killed by child predator Derek Percy. Photo / Facebook
Karen had just turned 11 and Gary was nine when Linda vanished near Melbourne's Luna Park on August 10, 1968 just a few days shy of her eighth birthday.
The trio had spent the day playing on the St Kilda foreshore not far from their Middle Park home, watching the boats and chatting to the youngsters fishing off the pier.
"I still remember it like it was yesterday," Karen, who is now 61, told news.com.au. "We walked up the pier and watched the kids fish and then a group of us found an old tin boat which we played in until the owner came and yelled at us to leave."
Before the siblings had set off that morning, their mother Jean Priest had told Karen she was in charge and to make sure they were home by 4pm.
"In those days there used to be a mini Luna Park, a little Luna Park side show by the pier and when the time came for us to go home, Gary and Linda didn't want to leave," Karen recalled.
"So, I left them there and started walking home, because I didn't want to get in trouble with mum for being late. About an hour later, Gary came home alone and said he couldn't find Linda.
"He said he'd been looking into a kaleidoscope and when he looked up, Linda was gone."
Deputy State Coroner Iain West (left) and Detective Senior Sergeant Wayne Newton hold vigil by the bedside of suspected child serial killer Derek Percy in 2013. Photo / News Corp Australia
The investigation was doomed from the start, with police waiting an astonishing four hours to respond to Jean's panicked call for help, by which time Linda and her abductor were likely long gone.
Initially, officers were not convinced a crime had even taken place, speculating the little girl had run away or accidentally drowned.
"Mum put in the call at around 6pm but police didn't show up until just after 10pm and when they did arrive, they had alcohol on their breath," Karen said.
"They didn't take it seriously. They thought she'd run away or fallen off the (St Kilda) pier and drowned. They didn't follow up witness accounts. Somebody had seen Linda with a man and someone else had noticed a man watching her rolling around on a hill.
"There were people who said they'd contacted police and never received a call back."
Unable to cope with her daughter's loss, Jean had a mental breakdown and attempted suicide.
During her recovery, the siblings were placed in state care and Karen remembers being shunted between children's homes, each one more horrible than the last.
For the next 40 years, the family remained in a state of limbo, battling untreated post traumatic stress and anxiety while the police investigation went nowhere.
From left: Gary Stilwell, 9, Linda Stilwell, 7, Laura Stilwell, 18 months and Karen Stilwell, 11 shortly before Linda's 1968 abduction. Photo / Facebook
"Back then there was no counselling and we felt very much alone," Karen says.
"We would sit in the house with the lights off and the blinds drawn to hide from the reporters hanging around outside," she said.
"One day the local reverend stopped by and told my mum that Linda had been abducted because my mother had left her husband. It was a very stressful, surreal time.
"We were so broken, so traumatised that it took us 20 years before we could bring ourselves to mention Linda's name and talk about what happened to her."
As the police investigation stalled, the media started making comparisons between Linda's disappearance and another unsolved mystery; the abduction two years earlier of Jane, Arna and Grant Beaumont from a beach in Adelaide, South Australia.
In July, 1969, just 11 months after Linda's disappearance, 12-year-old Yvonne Tuohy was kidnapped from Victoria's Westernport Bay and brutally murdered.
Police arrested Derek Percy almost immediately after he was found nearby still drenched in Yvonne's blood. He was charged with the schoolgirl's abduction, torture and murder but at his 1970 trial, was found not guilty by way of insanity and sentenced to jail indefinitely.
Karen Stilwell told news.com.au she believes Yvonne's death may have been prevented had police treated her sister's case as an abduction from the get go.
Derek Percy in his police mugshot after his 1969 arrest for the murder of Yvonne Tuohy. Photo / Supplied
"If they hadn't botched Linda's investigation so badly, Percy may well have been arrested before he had the chance to kill again and we might have had a chance at finding her remains," she said.
In a 1969 police interview, Percy was asked if he killed Linda Stilwell and replied: "Possibly, I don't remember a thing about it". He was never pushed for further details.
Police squandered another opportunity to extract information relating to the location of Linda's body when they sent a police officer and former schoolmate of Percy to ascertain his involvement in a number of unsolved cases.
The officer had written a note stating Percy had mentioned Linda Stilwell but once again police failed to pursue the lead.
Percy again conceded that it was "possible" he murdered Linda but could not remember for sure.
In 2009, Deputy State Coroner West found Percy was in St Kilda in the vicinity of Linda on the day she disappeared. In 2014, a year after Percy's death in hospital, the same coroner ruled Percy had caused Linda's death.
He remains the prime suspect in the 1965 murders of two 15-year-old girls at Wanda Beach in Sydney's south, the 1966 disappearance of the three Beaumont children in Adelaide, the 1966 unsolved murder of six-year-old Allen Redston in Canberra and the 1968 murder of three-year-old Simon Brook in Glebe in Sydney's inner west.
