THE young sailor slumped on the bed in the watch-house cell was crying with self-pity when an old school friend walked in. It was the first familiar face he had seen since his arrest two days earlier at the Cerberus naval base over the murder of a 12-year-old girl taken from a nearby beach.

But the "friend" was not there out of concern. He was now a young policeman and the homicide squad had sent him to persuade the prisoner to talk about past crimes. The suspect was Derek Ernest Percy — arrested trying to wash away his guilt and a dead girl's blood at the navy base, hours after Yvonne Elizabeth Tuohy had been abducted at Ski Beach, Warneet, and then molested, tortured and murdered.

When Percy grabbed her, he also tried to abduct her friend, Shane Spiller, 12, who escaped by threatening Percy with a tomahawk and running away.

The nature of the crime led detectives, including elite investigator Dick Knight, to conclude this was not Percy's first attack.

It was 1969 and Australia was reeling from a series of child abductions and murders over the previous four years.

Christine Sharrock and Marianne Schmidt were murdered on Sydney's Wanda Beach in January 1965; the Beaumont children (Jane, 9, Arnna, 7, and Grant, 4) were abducted in Adelaide in 1966; Allen Redston, 6, was murdered in Canberra in September 1966; Simon Brook, 3, was killed in Sydney in 1968; and Linda Stilwell, 7, was abducted from St Kilda in August 1968. All cases remain officially unsolved.

For nearly 40 years police have wondered if Percy was responsible for nine murders. Now, after a complex investigation involving old memories and new techniques, they have built a compelling case against Australia's longest-serving prisoner.

But in July 1969, the novice policeman was supposed to listen to his old schoolmate in the hope he would open up. And it almost worked. The policeman left the force 18 years ago to return to country Victoria and a quiet life. But when contacted by cold case unit detectives he immediately knew why.

Unprompted, he recalled his last conversation with Percy.

"He had been sobbing and was very distraught.

"He said, 'Looks like I've f---ed up this time'. I said, 'It certainly looks like it, Derek'.

"Derek put his head in his hands for a while, then he looked up at me again and he had tears in his eyes and panic written all over his face. He also looked at me with a plea for help."

The schoolmate gently asked: "Were there any others, mate?"

"Derek put his head in his hands and began to sob again. He said, 'I cannot remember'."

It was the same response he'd given two days earlier to homicide detectives over the Tuohy murder, until confronted with incontrovertible evidence.

The schoolmate, a policeman for barely six months, pushed on. "Well look, Derek, I'll ask you about some of the ones that I know about. You don't have to say anything. If you remember I will jot it down and it could be used in court."

Asked about Linda Stilwell, Percy again said his memory was blank but then made the first of several telling admissions: "Yes, I drove through St Kilda that day. I had been at Cerberus in the afternoon and was driving along the esplanade on the way to the White Ensign Club for some drinks."

Asked if he killed her, he said: "Possibly, I don't remember a thing about it."

Questioned on Simon Brook, he admitted being in Sydney at the time and said he had driven his brother to work, turning off at the railway cutting where the body was found.

The policeman, who cannot be named because of a suppression order, pressed him: "So you drove past the same spot in Sydney on the day Simon Brook was killed." Percy said, "Yes".

Question: "Do you remember if you killed him?"

Answer: "I wish I could. I might have. I just don't remember."

Question: "What do you know about the Beaumont children in South Australia."

Answer: "I was in Adelaide at the time."

Question: "You were what? You remember being in Adelaide when they went missing?"

Answer: "Yes."

Question: "Whereabouts were you when they disappeared?"

Answer: "Near the beach. But nothing else."

Percy was placing himself at each crime scene. Perhaps with more time and pressure he would confess, as he had done over the Tuohy murder.

But at that moment, the watch-house keeper told the junior constable he had no business being in the cell. The young copper said he was on homicide squad business, but when he turned back to Percy the spell was broken. The killer knew his former schoolmate was no longer a friend, but trying to find the secrets of his dark past.

In April 1970, Percy was found not guilty of Yvonne Tuohy's murder on grounds of insanity. He has never been charged with any other crime. But prison officers, psychiatrists, judges, police and welfare officers consider him the most dangerous man in Australia.

The policeman, now long retired, has never been in doubt. When he left the cell that day, another former schoolmate, called to Russell Street to make a statement, saw him. He was upset and shaking. "That f---ing bastard, I hope they hang him," he said.

FOR the cold case unit, going over Linda Stilwell's disappearance from St Kilda 36 years earlier was meant to be a case of tidying up loose ends to provide the coroner with a summary of facts. With no real chance of finding a body, the unit did not want to waste time needed for other cases. But when Senior Detective Wayne Newman started to delve in January 2004, he began to discover evidence that pointed to Percy.

For Newman, the "quick" investigation turned into a two-year quest linking Percy to baffling murders that have long seemed unsolvable. It would involve police from four forces, psychiatrists and forensic experts.

The investigators, many of whom were not born when the murders were committed, co-operated in a unique operation, codenamed Heats. To establish that Percy had killed more than once, detectives retraced the life of the quiet country boy who became a monster.

ERNEST PERCY was a NSW railway electrician for nearly 25 years before taking a job with the State Electricity Commission in Victoria, first moving to Chelsea, then relocating his young family to Warrnambool in 1957.

Ernest Percy's passion was sailing. His eldest son, Derek, just nine when they moved to Warrnambool, shared the hobby.

In 1961, Percy senior was promoted and the family went to Mount Beauty, near Bright. The Percys took caravan holidays, often travelling interstate to yachting competitions in their V8 Studebaker. Much later, police would track these holidays against their murder map from the 1960s, with intriguing results.

In 1961, Derek started at Mount Beauty High School. The school uniform included a green and gold striped tie. Other students noticed that Derek's tie was made of coarse fabric and not a perfect match for the school pattern — although it was close enough.

He became a friend of a local farmer's son who had also just moved to town and was one of few who liked Percy. Others found him intense, abrupt and at times unsettling. But no one thought he was dangerous. Yet.

When police from Operation Heats approached the friend, he told them: "One thing that stood out about Derek was that he was very intelligent. Most or nearly all of us at school had to work and study very hard but not Derek." He also noted that Percy was shy and never had a girlfriend.

Banned by his worried parents from playing football, Percy would sometimes borrow a friend's gear for the occasional game, convincing his mate's mother to wash the clothes so he would not be caught.

If the Percys were over protective, it was understandable. Their third-born, Brett, died from diphtheria when aged only 10 months. They were to have three surviving sons.

Derek earned his pocket-money working in the tobacco fields with friends — buying a second-hand red bike with racing "ram's horn" handlebars.

He carried his sharp knife everywhere, but in country Victoria that did not make him unusual. In the 1960s a pocket-knife was more a tool than a weapon, used to solve a problem rather than create one.

But when Percy used his to help a mate make running repairs to the sole of a shoe during a handball game, he showed a glimpse into his future.

"I remember Derek getting his pocket-knife out and telling me that he would cut (the sole) off … Derek began to cut the sole off my shoe and all of a sudden the blade went into Derek's left thigh about three quarters of an inch (about two centimetres). The blade went deeply into his thigh and I recoiled back in surprise.

"I was amazed that Derek just looked fascinated with what had happened. He didn't scream, cry or really show any sort of emotion that you would expect from someone with a knife in their leg.

"I thought his reaction was extremely odd," the friend said. "He seemed happy about it."

Kiewa Valley's hydro-electric plant was no Snowy Mountains Scheme but it gave tradesmen the chance to raise families in one of Victoria's prettiest spots.

There was little violent crime in the town of fewer than 2000 people, no need to lock houses or cars. But in late 1964, a small crime wave began: women's underwear began to disappear from clothes lines — and Derek Percy was rumoured to be the thief. Until then he had been a model student and a school prefect, but in 1965 his grades plummeted.

Ernie Percy threatened to sack any hydro worker who suggested his son was the phantom "snowdropper", but by late 1964 at least two locals knew that Derek was the culprit and that he was much worse than just a petty thief. He was dangerously disturbed and, they believed, a potential killer.

On a warm Sunday, two teenagers, Kim White and Bill Hutton, walked to a local swimming hole. There they saw what they thought was a girl in a petticoat. Then they realised it was Percy in a pink negligee.

"Well, at least it fits," one joked to his mate. But any humour was lost when Percy began to slash wildly at the clothing, then cut and stabbed at the crotch of a pair of knickers.

Hutton could see Percy's face. "I would describe Derek's eyes as being full of excitement, a glazed look, but I recall there was something very cold and sinister in the look," he told police much later.

The boys told a teacher the next day and were accused of making up stories. They confronted Percy but he denied everything. Most fellow students thought their story was fabricated. After all, Percy was the obedient student and his accusers loved a little mischief.

The following year Ernie Percy took a job with the Snowy Mountain Scheme and moved his family to Khancoban in NSW, but to allow Derek to finish school at Mount Beauty the teenager boarded with another family.

The woman who lived next door remembers how the new boarder would watch her hang out washing. One Saturday she took her daughters, then aged seven and nine, to visit a relative. When they returned they found the girls' wardrobes had been rifled through and their underwear and dresses stolen.

The mother reported the theft to the police, who asked her if she suspected anyone. She suspected Percy but did not want to say so, she admitted years later.

A few weeks later a local found some of the dresses in a bundle hidden under some bushes. With it was a girl's doll, with the eyes "blinded" and newspaper clippings of women in bikinis. The women's eyes were pencilled out and the bodies mutilated with razor blades. The slashes would match some of the wounds inflicted on the children murdered around Australia in the 1960s.

The blinded doll belonged to the girl next door to where Percy was living.

Percy moved from Mount Beauty to join his family in Khancoban after he failed his exams in 1965, a strange result for a student with an IQ of 122.

In his entry in the Mount Beauty school magazine he revealed a little of his concealed thoughts. His favourite saying was: "It depends." Perpetual occupation: "Isolating himself." Ambition: "Playboy." Probable fate: "Bachelor." Pet aversion: "Girls."

When Percy left Mount Beauty the "snowdropping" stopped, only to begin near his new home in Khancoban. There were also reports of a Peeping Tom.

While at Khancoban a neighbour found that Percy had lured her six-year-old daughter into the family caravan to sexually assault her. The girl's father decided to deal directly with Ernie Percy, who promised it wouldn't happen again. And it didn't. At least not there.

While both parents said they thought their eldest son was shy but normal, deep down they had growing fears.

One Mount Beauty local said that while Mrs Percy allowed her middle son freedom, the elder brother was kept on a tighter rein. "Derek had to get permission to go anywhere with us outside of school hours and she would question his intentions."

Ernie Percy would later tell NSW police he had once found Derek dressed in woman's clothing. The parents also found some disturbing sexual writings by their son and immediately burnt them. Later Percy's grandmother found letters filled with "rude" thoughts. Percy denied they were his. Again they were burnt.

Percy began writing down bizarre and violent sexual fantasies in 1965 — around the time his school grades collapsed. He continued the self-incriminating habit for years.

Much later police would allege the writings were plans for the crimes he was to commit and directly linked him to the series of unsolved child murders.

At the end of 1966, having repeated year 11, Percy was ready to leave school. His father also decided to leave the mountains to move into private enterprise. He invested his payout on a Shell service station in Newcastle.

Derek tried year 12 in a NSW school, dropped out, worked at the service station, and in November 1967 joined the navy, graduating top of his class a few months later.

Nearly four decades later, detectives started trying to piece together his movements around Australia over the crucial four-year period in the 1960s.

They knew the Percys often took their caravan to holiday near beaches during yachting regattas. They also could prove Percy was harbouring thoughts of molesting and killing children at the same time as the series of shocking abductions were carried out in four states and territories — and with one exception — all near beaches.

But was it simply a series of coincidences? How could a teenager from country Victoria grab kids hundreds of kilometres away? And how could a young sailor murder and return to his base undetected?

On a windy Monday — January 11, 1965 — teenage neighbours Marianne Schmidt and Mary Sharrock went to Sydney's popular Cronulla Beach area with Marianne's four younger siblings. After a picnic, the younger children stayed in a sheltered area at Wanda Beach and the two 15-year-olds started talking to a fair-haired youth.

Peter Schmidt, 10, saw his sister and her friend with the teenager. His brother Wolfgang, 7, had also seen them talking to the boy earlier. The youth had a knife in a sheath and carried a spear.

The girls' mutilated bodies were found the next day, partially buried near a sand dune.

As in the Tuohy case, the victims were taken from the beach and dumped nearby. The crotch area of one of the girls' bathers had been cut. Percy had been seen slashing female underwear at Mount Beauty in late 1964 — just weeks earlier.

Some people remembered that the Percys had gone to Sydney for a holiday that summer. The mother of one of Percy's closest friends in Mount Beauty told detectives that she had always suspected that Percy might have been "a suspect in that case".

Ernie Percy took holidays to coincide with yacht races around Australia. That summer the national yachting regatta was at Botany Bay Yachting Club — near Wanda Beach. Percy's grandparents lived walking distance from the West Ryde railway station where the two girls caught the train.

After police arrested Percy at Cerberus, they found a diary in which he described his urges to sexually abuse, torture, murder and mutilate children. They also found drawings of naked children and women.

In one excerpt, Percy wrote he would force one of his victims to drink beer. Autopsy results showed that Mary Sharrock had a blood alcohol reading equivalent to drinking about 300 millilitres of beer.

In his murder blueprint he wrote about abducting and killing "Two girls at Barnsley", a NSW beach in northern NSW. Police believe it was code for Wanda Beach.

It was 1966 and Percy had moved to Corryong High when classmate Wayne Gordes decided to tease the new student after he saw the obvious resemblance to the photo-fit. "I jokingly thought to myself 'That's Derek', because of the description and I knew that they went to a beach in Sydney.

"A group of us were standing in the quadrangle when Derek Percy walked past. I said, 'We know it was you that killed those girls in Sydney. You have the same haircut and we know you were there.'

"With that Derek went berserk. He said, 'Don't you say that' … I think he wanted to fight me for what I had said. I had never seen Derek behave like that before."

ON WEDNESDAY, January 26, 1966, the Beaumont children — Jane, 9, Arnna, 7, Grant, 4 — caught the bus from their Somerton Park home to Glenelg Beach, Adelaide. They left about 9.45am; their mother, Nancy, expected them home about midday.

A friend of Jane's saw them sitting near the Holdfast Bay Sailing Club about 11am. A man was seen talking to them and at 11.45am the children bought a pie and two pasties from a bakery in Jetty Road.

The man almost certainly gave them cash for the food as they paid with a £1 note — more money than their mother had given them. They were never seen again.

The suspect was described as in his 30s with light brown, short swept-back hair parted on the left side, a thin face and clean-shaven. He was suntanned and wearing blue bathers with a white stripe down the side.

Could it have been Percy? He was only 17 at the time but was sometimes mistaken for being older. His writings showed he planned to give food to the children he would kidnap before killing them. The Beaumonts were in the age group Percy fantasised about and they went missing from the beach, as did Yvonne Tuohy, Marianne Schmidt, Mary Sharrock, and Linda Stilwell.

Some elements of the description fitted Percy, some didn't. The original sketch of the suspect was done by a non-police artist and is not considered accurate.

Was Percy in Adelaide? He told police he had been there on holiday but couldn't remember when. His brother confirmed they had been there. The mother of one of Percy's friends told police: "I can also recall that Derek travelled to Adelaide on holidays by plane on one occasion."

Asked by detectives in 2005 if he was in Adelaide when the Beaumonts went missing he answered, "I don't know".

They then asked if he was blocking out thoughts "because something horrible happened in Adelaide and you don't want to remember it?" and he said it was possible.

Five days after the Tuohy murder he was interviewed by prison psychiatrist Dr Allen Bartholomew who found Percy had the capacity to repress memories of the crimes he committed. He said that if Percy had been arrested a week after the murder he would no longer have been able to recall what he had done.

Without bodies or a confession, Percy heads a short list of suspects for the Beaumont children. Evidence is too scanty to prove or disprove his involvement but the similarities of the crime with Percy's modus operandi are striking.

Detective Sergeant Brian Swan from Adelaide's major crime investigation branch said Percy remains "a person of interest in the disappearance of the Beaumont children".

And Dr Bartholomew observed after interviewing Percy: "It is not beyond the bounds of possibility that there is some other great harm been done in the past and there is no way of knowing it."

ON SEPTEMBER 27, 1966, Allen Geoffrey Redston, 6, left his home in the Canberra suburb of Curtain to go to the nearby milk bar to buy an ice-cream.

The following day his body was discovered concealed in reeds by a local creek. The body was hog-tied and had plastic wrapped around the throat.

A police investigation found that in the days leading up to the murder, a fair-haired teenager had been forcing boys to the ground, tying them up and placing plastic over their heads in an apparent attempt to asphyxiate them.

The identikit closely resembled Percy and the suspect was riding a distinctive red pushbike with "ram's horn" handlebars — the type Percy rode at Mount Beauty and took with him on caravan holidays.

When Dick Knight questioned Percy in 1969, he confirmed taking a family holiday in Canberra in 1966. Police established he had a Canberra relative but have found no records to pinpoint the exact date of the holiday.

Percy's writings detail using plastic and his plans to tie up and asphyxiate victims. Both Redston and Tuohy were tied and gagged when their bodies were found.

Percy was the product of an otherwise stable family. But there was a secret. When Derek was young and being cared for by his grandmother, she would use a bizarre form of punishment: she would lock him in a room and hog-tie him — feet and hands bound the way little Allen Redston's were.

One item found at the crime scene puzzled the original investigators. Along with other material used to used to bind the child was a tattered green and gold striped tie. It was similar to the Mount Beauty High School ties but was made of a distinctive coarse cloth, like hessian. It matched the school tie Percy no longer needed after transferring to Corryong High earlier that year.

That is one reason why federal police say that Percy cannot be eliminated "as a person of interest in relation to the death".

AFTER three months in the navy, Percy was posted to the aircraft carrier HMAS Melbourne on March 9, 1968. But the ship was in Cockatoo Dry Dock at Sydney Harbour for a year-long refit and the junior sailor was assigned fire sentry duty.

He lived at the naval base at nearby Garden Island and commuted through the suburb of Glebe to the dock. On Saturday, May 18, 1968, Simon Brook, 3, went missing from the front yard of his family home in Alexandra Lane, Glebe. The house was next to Jubilee Park on Sydney Harbour, close to beach and yachts.

A truck driver later said he'd seen a boy matching Simon Brook's description holding a young man's hand near Jubilee Park.

The mystery man was well-groomed with a neat haircut, and an identikit image has a startling similarity to a photograph of Percy in his school year book.

The little boy's body was found behind a building site about 350 metres from the Brooks' home. There were several signature injuries similar to those inflicted on Yvonne Tuohy. When police examined the scene they found two Gillette razor blades probably used in the attack. The same brand was issued to sailors.

But the most damning evidence comes from Percy's own hand. In his diary, he wrote of abducting and killing a three-year-old "baby" and described in detail the exact injuries inflicted on Simon Brook. Detectives say it is a virtual confession.

When Dick Knight interviewed Percy in 1969 he asked him, "Did you kill Simon Brook?", and Percy said "I could have". When Percy talked to the young policeman who was his old schoolmate, he admitted he had been in the Glebe area at the time "turning off at the railway cutting where the body was found".

Only someone with a detailed knowledge of the area would know that Simon Brook lived near a railway cutting, and if Percy turned off at the railway cutting he would have driven straight past the Brooks' street.

Crime profiler Detective Senior Sergeant Debra Bennett concludes "there is all likelihood that the offender for Simon Brook's murder and the offender for Yvonne Tuohy's murder is one and the same".

And NSW Coroner John Abernethy agrees. A new inquest was held in 2005 and after just two days he found the evidence so compelling he closed the hearing and referred the case to the Director of Public Prosecutions. Percy was flown to the inquest but chose not to give evidence on the grounds of self-incrimination.

Abernethy said he believed there was a "reasonable prospect … that a jury would convict a known person in relation to the offence". Charges might still be laid.

LINDA STILWELL was four when her family arrived in Melbourne from England on the migrant ship the MV Fairsky in April 1965. Linda was the second youngest of four children. For her mother Jean and father Brian the new start could not save their marriage. In July 1968, Brian left for New Zealand with their youngest child, Laura. Jean stayed in Melbourne with the other three, took a job at an Albert Park hotel and moved into a flat in nearby Middle Park.

On Saturday, August 10, 1968, she told her children to stay home while she went grocery shopping. But the lure of the beach was too much for the two eldest, who wanted to explore the new neighbourhood.

When Mrs Stilwell arrived home about midday, Karen, 11, and Gary, 9, had left. She dressed Linda, 7, and told her to go and find her brother and sister to bring them home for lunch. Three hours later Karen returned to say Gary and Linda were fishing on the St Kilda Pier.

About 4pm Gary returned, saying Linda had gone to Little Luna Park to "look at the rifles" with some boys. His mother sent the boy back to find his sister but he came back saying he thought she might have gone to the police station to collect some fishing rods.

Stilwell rang the police and was told that two boys had been in to get the rods but there was no sign of a little girl. Three small boys told police they had last seen Linda at Little Luna Park.

Two days later a woman contacted police and said she had seen a girl matching Linda's description rolling down a grassy hill near the Lower Esplanade. She said she saw a man near her. She described him as having an olive complexion, thin features and wearing dark clothing.

She said the man was wearing "a deep navy blue, almost black, spray jacket, similar to that worn when sailing. The man was sitting with his legs crossed looking out to sea quite intently, but appeared relaxed."

About 80 suspects were questioned but no leads came up. Linda was never seen again.

Percy had transferred to the troop ship HMAS Sydney (based in Melbourne) on July 1, 1968, but was on leave for 18 days from August 5, five days before the abduction.

After Percy was arrested for the Tuohy murder the following year, the woman witness opened the paper to see the picture of the suspect. He was wearing a dark spray jacket. "I got the biggest shock of my life. This was the same man that was sitting on the park bench the day that the little Stilwell girl disappeared in St Kilda," she said.

About two years ago, when Percy's arrest photo was again published, identifying him as a suspect in a series of unsolved murders, the witness came forward again. "I am absolutely sure that the man I saw sitting on the park bench the day Stilwell disappeared is the same man," she said.

When Percy was asked by his policeman friend about Linda's disappearance, he said that he had driven through St Kilda that day. Asked if he was the killer, he said: "Possibly, I don't remember a thing about it."

In his belongings police found maps he had marked. One was in West Ryde near where the Wanda Beach victims caught the train, one was marked through Glebe where Simon Brook was killed, and another was marked with a line past the spot where Linda Stilwell was last seen.

Victoria's State Coroner Graeme Johnstone is expected to hold an inquest into her disappearance. Whenever Linda Stilwell's mother, Jean Priest, moved house, she would go to the homicide squad to pass on her new address in the hope that one day she would get the call that there had been a breakthrough. But over the years she found the new generation of detectives no longer even recognised her daughter's name.

Operation Heats has given her new hope. "It has helped me to know that people like (Senior Detective) Wayne Newman have cared so much and done so much work," she said last week. "You learn to live with what has happened but you can never forget."

All she wants now is for the evidence against Percy to be produced at inquest. "Then I will be able to put a name to the face … I just hope he would finally admit what he has done."

Derek Percy was surprisingly chatty when Operations Heats investigators questioned him in early 2005. Balding with a long grey beard, he has retained his striking cold blue-eyed stare. He chatted happily while drinking tea with three sugars and nibbling on a cheese and tomato sandwich.

He is serving an indefinite sentence under the insanity verdict, but he has previously applied for a minimum term — an appeal that has failed because he is considered a danger to the community.

He still hopes to be released, and a confession that he had killed many times would destroy that dream. Having received a navy pension since his arrest, he is one of the richest inmates in prison, with nearly $200,000 in the bank.

Detectives were to ask him 1535 questions. He could recall details of his childhood but when asked about the murders he grew quiet.

NSW Detective Sergeant Adam Barwick said that when Percy was asked about the Brook murder he was "visibly different, in that his lip quivered, and his answer was 'I can't remember'. I formed the opinion that Percy was lying when answering these questions."

Police believe that Percy's claim that he cannot remember is self-protection rather than self-deception. They think he is bad — not mad.

Ironically, detectives say, the charade that he was insane at the time of the crimes is in the public interest. If he had stood trial and been convicted in 1970 for the murder of Yvonne Tuohy he would have been released years ago … and would inevitably have struck again.

THE LIFE AND CRIMES OF DEREK PERCY

• 1948, SEPTEMBER 15 Born in Strathfield, NSW
• 1954 Attends primary school, Missions Point, NSW
• 1956 Family moves to Chelsea
• 1958 Moves to Warrnambool
• 1961 Moves to Mt Beauty
• 1964 Seen slashing women's clothing. A suspect for "snow dropping".
• 1965, JANUARY 11 Wanda Beach murders. Mt Beauty locals see resemblance between Percy and identikit of suspect.
• 1965 Starts keeping graphic diary. School grades plummet. Fails year 11.
• 1966 Moves to Khancoban. Molests young girl.
• 1966, JANUARY 26 Beaumont children go missing. Mt Beauty residents recall Percy holidaying in Adelaide. Percy later says he was in Adelaide on the beach on the day.
• 1966, SEPTEMBER 28 Allen Geoffrey Redston, 6, is abducted and murdered in Canberra. Percy later tells police he has holidayed in the capital but can’t recall details. In the days leading up to the murder there are reports of a teenager attempting to suffocate children in the area. The description fits Percy. Suspect rode a bike similar to Percy's and victim was bound with a tie similar to Mt Beauty school uniform tie.
• 1967, NOVEMBER 25 Joins navy.
• 1968, MARCH 9 Stationed in Sydney.
• 1968, MAY 18 Simon Brook, 3, abducted in Glebe. Percy writes in his diary of abducting and murdering a three-year-old. The details in the diary match the fatal injuries inflicted on the victim.
• 1968, AUGUST 5 Goes on 18 days’ leave from navy. Tells police he stays in Melbourne.
• 1968, AUGUST 10 Linda Stilwell abducted from St Kilda foreshore. Percy on leave at the time. Had a map that was marked in the area she went missing and told police he was in the area that day.
• 1969, APRIL 1 Stationed on the Cerberus.
• 1969 Attempted abduction of a 12-year old girl on a bike near the Cerberus base. Victim later identifies Percy as the attacker.
• 1969, JULY 27 Abducts and murders Yvonne Tuohy from Ski Beach. Arrested later that day. Police find his diary filled with violent sex fantasies.
• 1970 Found not guilty of the Tuohy murder on the grounds of insanity. Jailed for life.