51

How accurate is Elaine's memory? I wonder. For a woman in her eighties she is astute, switched on, but on some subjects she is vague and unsure. I don't know how much detail she has on Yvonne Tuohy's murder and so I tread carefully. 'Elaine, do you know the name of Derek's victim?'

She shakes her head. 'No.'

'Do you know any details of what happened to her?'

'No. I don't dwell on it. I only know the scarce details.'

'Do you know the girl was twelve years old?'

'No. I didn't know that.' This seems inconceivable at best, ridiculous at worst. Heartbroken and bewildered, Elaine had sat outside the court for six long days while Derek was on trial. She read the newspapers. She spoke to police. She would have had to be blind and deaf to have missed the sordid details; either that, or hiding behind what Simon and Garfunkel called the 'Sounds of Silence', I wonder, too what she understands of Derek's memory. 'I've got no idea what his memory is like,' she says. 'It's never come up for me to have to test his memory.'

She recalls a conversation she had with her son, Lachlan. 'He said, how would Derek have the sense to get away with the Simon Brook murder? And I said to him, he wouldn't.' Derek's IQ is far above the national average. How hard would it be to get away with the murder of a defenceless three-year-old boy? By the time of Simon's murder, Derek had learned to drive in his mother's Datsun. He was on weekend leave. Did he borrow her car that morning? He initially told police that he drove Lachlan to work that day in Glebe before he changed his story and said he didn't know what he would have been doing driving around Sydney when he didn't think he even had a car at that stage. How does Elaine explain his first admission? Her answer is flatly simple: 'He lied to the cops.'

We move through what Elaine and Ernie knew of Derek's odd behaviour at Mount Beauty and Khancoban. She is adamant that she knew nothing of the snowdropping rumours. 'Definitely not. No, I didn't know about that.' In a small place like Mount Beauty, filled with gossiping women and adolescents who thought Derek strange and working class blokes with little patience for those sorts of shenanigans, surely the dogs would have been barking these rumours? How could she not have heard about it?

'What about the incident in the caravan with the young girls?' I ask. Both she and Ernie, she admits, knew about that incident. 'I didn't say a lot to him about it, but Ernie grounded him. I went to the door of the doctor with him but didn't go in. Anyway, the doctor passed it off as nothing serious, a thing he would grow out of. We did what we reckoned was enough to set things right. We did what we thought we had to.' She shrugs. 'We thought it was a one-off.'

This does not stack up against what Ernie Percy told Detective Bradstreet when he interviewed him at the Shell Auto Port in Wallsend on 13 August 1969. 'Mr and Mrs Percy arranged for Derek to attend Dr Webber's surgery, and told the boy to ask the doctor to contact them if any treatment was required,' Bradstreet wrote. 'The parents did not hear from the doctor and in actual fact they did not know whether Derek attended the surgery or not, although the suspect told them that he had and that the doctor said that in time he would grow out of acting in such a manner.' The parents did not hear from the doctor and in actual fact they did not know whether Derek attended the surgery or not. Why would Elaine tell me such a blatant untruth?

Elaine grimaces when she recalls hearing about police finding Derek's writings in the warehouse. 'They didn't bother to warn me about it. I just saw it on the television news.' Again, she says, her world was changed in an instant. 'I had no one to talk to about it. My other sons won't discuss it.' She fretted for weeks, sleeping badly and quietly cursing police for not giving her the courtesy of telling her what they had found. What Elaine heard disturbed her greatly. 'I was so disgusted with what was in that warehouse, I thought, this is the living end. I didn't send Derek a Christmas or birthday card after that.' Elaine only got in contact with Derek after he sent her a birthday card, and she wrote him a perfunctory card back, signing it, Love Mum.

'What would you say to him now, Elaine, if you talked to him?' I ask.

She sighs. 'I'm so disgusted and disappointed in him that all I would ask him is, why, Derek?'

'Is he insane, do you think?'

'Well, he wouldn't do what he did for fun, would he? You'd have to be out of your mind, wouldn't you?' It sounds like the last refuge of a bewildered mother with nowhere mentally to go, grasping at a reason for unfathomable behaviour. 'My aunt's child committed suicide many years ago so I reckon that there's a mental streak somewhere in our family. I mean, he wouldn't do what he did for fun, would he?' she repeats.

Elaine hasn't seen Derek since 2000, the year before Ernie died. She hates flying and to travel a long distance by road is out of the question at her age. 'Ernie was heartbroken about what had happened and it wore on him heavily. We just couldn't understand why.'

'What about Lachlan and Leon, now they are adults? Do they see Derek?'

The chess games Percy played with Lachlan had long stopped. Lachlan visited his brother once but vowed never to go again. His marriage broke down, partly as a result of the ongoing trauma in his family, and he no longer admitted to anyone that Derek Percy was his brother. Embarrassed and ashamed, Lachlan distanced himself completely. Leon has never married; now in his late forties he shares a house with Elaine and keeps busy with cars, cricket and computers. Though Elaine describes him as an 'absolute wonder', he refuses to talk to her about Derek. It's all best left alone, he says. All of it.

I glance at my watch. Elaine and I have been talking for six hours. 'I've taken up a lot of your time,' I say, standing to leave. 'I'm going to get out of your hair now.'

'No, don't say that,' she admonishes. 'I've enjoyed having you.' She presses a crocheted doily she has made into my hands. 'Here, have this. Something from me.' She stands and sees me to the door, both yapping dogs in full flight behind.

'Do you have a photo of Derek in your purse?' I ask her.

'No,' she answers, immediately. 'I don't want people to know he's my son. To be honest, I'd be grateful if someone rang and said he had died in prison. He's had a hell of a life but he's brought it all on himself. I'm being selfish, I know, but it has taken its toll.'

On the long flight home, I ponder what a sad life Elaine has had, in many ways; the heartache of losing one son to diphtheria and another to prison. I go over my notes of the interview. Some of the things Elaine told me just don't seem to stack up. But what at first felt like a good 'get' in journalism now feels like I am betraying an elderly woman's trust. It makes me uncomfortable; betrayal is not in my nature. I go over and over in my head the terms on which we agreed to talk. You understand this is your opportunity to tell your side of the story, but that I am not Derek's advocate? You understand that this story is about him and his possible involvement in other child abductions and murders and that whatever I find, I will use? And she had agreed. She understood. I start checking some facts against what Elaine has told me.

Derek wanted to watch the English cricket team play. Where did they play over the summer of 1965/66? I check the internet. England had its third test in Sydney from 7 to 11 January 1966. The fourth test was in Adelaide, 28 January to 1 February 1966. The Beaumont children disappeared in Adelaide on 26 January. Was Derek, a cricket fanatic, in Adelaide with his family to watch that test, or on his own? Would Elaine, the woman described by everyone who met her as an overprotective mother, tell me the truth if he was? Has she established an elaborate alibi for her son?

I call Tim Attrill. 'Elaine Percy told me that a friend of Derek's committed suicide on a ship,' I say. 'You joined the Queenborough before Percy, at the end of June 1968 and you left the day before he did, on 7 March 1969. Then you started at Cerberus with him on 24 March. Do you recall a suicide on that or any other ship during the time he served?'

'Not that I know of,' Attrill comments. 'If you ask me, it's bullshit. There was certainly no suicide on the Queenborough. The only thing I recall is a mate of mine having a seizure on that ship when we were alongside at Garden Island in Sydney. He was conscious when they carried him past me and Percy was working on the iron deck, wearing his gunbelt as usual. Every ship carries a steaming log and the captain is obliged to note all incidents on board. Check the steaming logs for the Melbourne and for when he was based at HMAS Kuttabul. Contact Allen Inderwisch, who is a researcher at the Cerberus Museum. He may be able to help.'

Inderwisch returns my call within the hour. 'I haven't heard of any suicides on ships or bases during that time,' he says, 'but I'll check for you. Leave it with me. I'll get back to you after the Christmas break.'

He is as good as his word. 'I've been through all the records,' he says. 'There were absolutely no suicides at all in the time that Percy served. But you need to check Seapower Centre for deaths and for ships' logs.'

The senior researcher at Seapower checks the records for me. From what he can see, there were no accidental deaths reported during his time, either, although deaths and injuries of navy personnel in Vietnam are mentioned, as are deaths of long-serving members of the RAN.

I tell Attrill about my conversations with Elaine Percy, how she shut down when she heard any hard facts about the Tuohy murder and was adamant that Derek could not be responsible for any other child crimes. He isn't surprised. 'Derek shuts down, too,' he says. 'His old defence is that he "can't remember". Perhaps, he adds somewhat facetiously, it 'runs in the family'. What he means, I think, is: don't ever be surprised at the lengths people will go to protect their loved ones. And I remember my own mother's adage: never come between a lioness and her cubs. 'I used to tell young police officers that when they were dealing with the family of a suicide victim, they should expect that most of them would demand a murder inquiry,' Attrill continues. 'That's because they find it so hard to accept that if it is suicide they may have contributed in some way or could have prevented it. There is always a fair degree of self-rationalisation involved. Similarly, if people lie to themselves long enough, they'll convince themselves they're innocent. That's why gaols are full of innocent men.'

'Tim, if you know that someone has deliberately hidden or destroyed evidence when police have a warrant to search, what can you do?'

'We couldn't take that person in for questioning. There is no obligation for people to cooperate. If we suspect someone was hampering inquiries or destroying evidence we would have to prove it and then pursue a charge of perverting the course of justice. We would be guided by legal advice.'

Elaine has promised she will look for notes she has written that prove that Derek was not in Adelaide in January 1966. Shortly after I arrive home, a letter arrives from her. 'I've searched countless times for those notes, but they must have got thrown out somehow.' I call her again, as she has invited me to do. This time, she is slightly more cautious on the telephone.

'Elaine, a recurring theme in the unsolved child murders from 1965 until Derek was arrested in 1969 was that the children were abducted or killed at or near the beach,' I start. I roll through the names, now a familiar routine.

'Yes,' she said, guardedly. 'What has that got to do with Derek?'

'I'm hoping you can tell me that. Can you remember anything from his childhood where there was an incident around water?'

'No, I can't. He had no connection with water.' She emphasises the middle words, to underline her exasperation. No connection with water. 'There was a communal pool at Milsons Point when he was about seven years old but he never went in it.'

'Is it possible he was molested at the beach or near water?'

'You wonder if anything devastating happened to him.' Her answer surprises me: just two months earlier she had assured me nothing had happened to him as a child. 'We knew everyone in the small communities, like Warrnambool, where there was a yacht club. There were no incidents there, but maybe something happened and it never came up.'

'You mean that you didn't hear about it?'

She sighs. 'It's possible.'

Is it also possible, I wonder, that he may have told someone and it was deemed better to say nothing? Or, worse, he wasn't believed? Don't tell fibs, Derek.

'Anything else you can think of?' I'm starting to struggle, trapped in a maze of awkward questions and perfunctory answers. 'Anything at all? What was he like at swimming?'

'Oh, he wasn't a good swimmer. He didn't like water, particularly.'

'He didn't like water? But he went sailing all the time with the family. You've told me all the boys were practically born in boats. What do you mean? Why didn't he like water?'

Derek, she finally tells me, was totally traumatised by his first swimming lesson when he was six years old. 'I took him to a Learn to Swim pool in January, in the school holidays,' Elaine says. 'There was a swim instructor and a lot of other kids in the pool who were enjoying their lesson. But Derek refused to get in the water. He was frightened – terrified, actually – and threw a tantrum. Yelling, crying, upsetting the other children. The teacher was not impressed at all.'

'What did you do?'

'I took him home, of course. I wasn't very happy with him.'

'Did he embarrass you with his behaviour?'

'Yes, you could say that.' We have not discussed Derek's unpleasant fetish for faeces and urine but now it is important and I am sure she already knows, but does not wish to admit it. 'Elaine, did Derek wet his pants that day out of fear? Or dirty them?'

'How would I know?' she retorts. 'It was more than fifty years ago!'

'Please think about it.'

'No, I wouldn't think so. I don't think that happened.'

'But is it possible?'

'Yes, I suppose so,' she concedes. 'Yes, it's possible.'

'Did you punish him for his naughty behaviour?'

'Well, he would have been given a severe talking to. We didn't physically knock him about, if that's what you mean by punishment. What's the good of that?'

The mental picture is now very clear: a small child in his swimsuit being lowered into the water and into the instructor's waiting arms. Baulking, shying back, trembling, making a scene. Elaine embarrassed, the instructor furious, the other children in their skimpy swimsuits tormenting him, laughing, pointing and Derek being ordered to stop this nonsense, to get in the water. Screaming, now, petrified; yelling 'No! No!', kicking his feet as the telltale urine trickles down his legs and Elaine, red-faced and angry, bundles him into a towel and hustles him out the pool door.

What happened when they got home? I wonder. Did Elaine tell Ernie that he had played up? How severe was the punishment? Who else was in the house that day? Was he made to feel guilty and inadequate for not being like the other children and getting in the pool? Is it possible that the seed of his later behaviour was sown from that time? Fear, embarrassment, anger and punishment embedded in his memory with half-naked children, water and revenge?

I wonder why Elaine didn't think this was important to mention earlier.

Shuffling through my early notes, I come across the comment I penned to myself after I read the deposition from Frank Percy and Beryl Couch that Derek had been badly neglected as a child. Normal childhood, my arse. What caused Percy to develop such an obsession with gagging children to silence them and tying them up so they could not escape? Was that because his grandmother had hogtied him in a dark cupboard? Why such an obsession with death? Why babies? Why children? Why pregnant women? Why excreta and urine? Did he dirty himself when he was tied up? Did he dirty his pants in fear when his father yelled at him? Did the idea germinate the day he went to his brother Brett's funeral? The brother whose nappy he had changed?

Brett was just a ten-month-old child whose sudden death undoubtedly sent Elaine and Ernie into quiet, bottomless grief. Suddenly the household was plunged into gloom. Did Derek, seven years old, feels abandoned, his world turned upside down? His birthday party had been fun but there is no fun now and he can't get his mother's attention. Did he blame himself? Elaine knows she did not go to the crematorium, but she can't remember if Derek accompanied his father there after the service. Is that what triggered his trauma, the sight of his brother's tiny coffin disappearing through the curtains? Brett's name was barely mentioned in the household after he died – what's done is done; we can't undo it – but it is possible, according to psychiatrists who claim Derek had developed his fantasies up to eight years before his arrest, that the year Brett died – 1962 – was the year they started. Vivid, terrible fantasies, including roasting a baby on a spit. How traumatised was the young Derek, imagining his baby brother being sent through the curtains to burn, an image so dark and powerful that it stayed with him to adolescence?

Did he feel powerless as a child, less so after his parents learned of his predilection for sordid thoughts toward children, once they read the grim evidence that their eldest son, the boy who was once a prefect, the product of their perfect marriage, was a sexual sadist aroused by psychological and physical suffering of his victim, and a paedophile with homosexual leanings? Was he a kindred spirit to Russian serial killer Andrei Chikatilo, who admitted at his trial in 1992, where he was found guilty of murdering fifty-two women and children, that 'I felt a kind of madness and ungovernability in perverted sexual acts. I couldn't control my actions, because from childhood I was unable to realise myself as a real man and a complete human being.'?

Derek was not allowed to play football, had to tiptoe around the house lest he woke his father and incurred his wrath. Was this why murder became his ultimate expression of power, the power of life over death? I'll get your attention. I'll show you. They can't understand what has gone wrong: Lachlan has grown up in the same household, with the same opportunities; he is normal. Why is Derek such an aberration? Was he impotent, taking out his sexual frustrations and rage on the most vulnerable in our society, children?

I read and re-read Elaine Percy's interview notes, troubled by something I can't quite grasp. What is it about her story that seems to be missing? If Derek had such a peachy childhood, what the hell went so wrong?

I meet with Kossie, an old friend and former police officer, to ask his advice. 'Something isn't adding up,' he agrees. 'There are bits missing. If a story doesn't gel, the person is lying, has genuinely forgotten, has created an illusion about events or has built an alibi to protect someone.'

He runs through some scenarios. Was Derek always trying and failing to please his mother? Did he wet or soil his pants when he was frightened? Who frightened him? Mum? Dad? Other children? Gran? Did he constantly seek approval because his mother wanted a girl, expressed as Derek being too pretty to be a boy? Did she treat him as a girl: don't play football, don't get dirty. Was his fantasy to cut off a young boy's penis imagined in order to satisfy a subconscious desire to be a girl, later expressed through cross-dressing? Was he punished because he pooed his pants, or did he poo his pants because he was punished? Did this boy, described in a Grade Two report as a 'slow worker', have faecal accidents, and did faeces then become his weapon of power, his way of saying up yours? Did he have a fetish for pregnant women because they are the ultimate female, carrying the ultimate innocent child – an unborn baby?

'Whatever was going on here,' Kossie says, 'you need to wonder at how dark a mind can get. This bloke, for whatever reason, developed a major oil leak. Talk to a forensic psychiatrist.'

Police who have dealt with Elaine Percy do not buy her story that she did not know about her son's activities. 'Make no mistake, she is an aloof, dominating and controlling matriarch,' one, who asks not to be named, tells me. 'As soon as Derek's name is mentioned, she becomes defensive and protective. Still waters run deep in that family.' Elaine, he says, paints the picture of her marriage and the household as close and happy, but there wasn't a lot of love or open affection. 'It was conservative and restrictive. I reckon they knew there was something very strange about Derek from an early age, and that's why they watched him like a hawk. They would have had great difficulty coping with Derek's strangeness. His overt acting out of sexual fantasies, his robotic, psychopathic condition and preoccupation with stabbing started when he reached puberty, but the question is: what happened in his childhood for him to be like this in the first place? He may have been given clothing, food and shelter, but what about emotional neglect?'

Percy, he says, was in the perfect position to move about, undetected. 'Here is a young man with no prior convictions, obsessed with his sick fantasies, who had the opportunity to travel, either with his family, while he was in the navy and when he was on leave. Think about his nicknames: the Spook, the Ghost, the Phantom. Someone who earns that sort of nickname can easily go into a place, commit a crime, come out again unnoticed and then blend back into the community as if nothing has happened.'

From the word go, he says, police have tried to eliminate Percy from their inquiries, but they just can't. 'With the Beaumont children, for example: while we can't categorically place him at Glenelg that day, his fetish for multiple children, the extreme rarity of the Yvonne Tuohy crime and the opportunistic manner in which he carried it out, the beach setting, his ability to move in and out of places and his age – seventeen – all point to a very strong possibility that he could be the perpetrator.'

Elaine, he says, does not want to take any blame for Derek's actions, conveniently hiding behind her dead husband. 'She tells us that if Ernie was still alive he might be able to tell us more. That, of course, is no good to us at all and it gives Elaine the opportunity to wipe her hands of any responsibility. It is very doubtful that Percy himself will ever tell us what he knows. The fear is that Elaine, too, will go to her grave protecting her son. We think that she holds the key to it all.'

She holds the key to it all. In early January 2009 I call Elaine at her home again. 'I'm cranky today,' she tells me, sighing. 'It's stinking hot here and I can't get any relief from the heat. No good can come of this book, dredging up the past like this. No good can come of it.'

'Elaine,' I say to her, 'you have told me countless times that you know for a fact that there is no way that Derek could have been in Adelaide on 26 January 1966 because he was with the family on the way back to Khancoban. And you remember that trip so clearly because he went to watch the English play at Newcastle on the same day that his school Leaving results were published in the newspaper.'

'Yes.'

'Are you positive it's the same day?'

'Yes.' The answer is an elongated sigh, with more than a hint of chagrin. 'We've been over this. Why do you keep asking me the same questions?'

'I have checked the newspaper, Elaine, and those Leaving results came out on 19 January. The English cricket team played in Adelaide from 28 January. They played a three-day match in Newcastle on 14, 15 and 17 January. They did not play in Newcastle on 19 January, which is when you insist Derek watched them. In fact, they were playing in Launceston, Tasmania, on that day.' Local Newcastle historian and cricket buff Stephen Brown, who checked the newspapers for those days for me, had assured me that the MCC game was big news. When the English came out to play Australia, he said, it was akin to the Olympic Games. Spectators only got the chance to see them once every four years and kids lined up, like today's paparazzi, to beg for autographs, assailing the players as they walked into the changing rooms. A cricket fanatic would travel anywhere to see them play. The Newcastle Herald frontlined with 'MCC Welcomed!' on the first day of play, relegating news of a three-day truce in Vietnam to the second page.

Elaine will not be swayed from her certainty that the cricket and the results came out the same day. 'Rubbish,' she shoots back. 'I've got a photograph somewhere that had some signatures on it that Derek got on that day.'

'Well, that's great. Could you find that picture and send it to me? It doesn't prove that Derek couldn't have been in Adelaide seven days later and it is a physical impossibility that he was at a Newcastle match on 19 January, but it does prove, at least, that your recollection that he was in Newcastle watching the cricket – just before the time you said that the family drove back to Khancoban when you heard about the Beaumont children on the radio – is right. And you must have not driven straight home to Khancoban; if Derek saw the match on 17 January, it had to be nine days later that the report came on the radio. Please try to find that photograph. I'll call you in a few days.'

Elaine can't find that photograph. 'I must have tossed it out,' she says flatly when I ring her three days later. She is so sure that her dates line up: could it be that she is just elderly and forgetful, that in her determination to prove that her son could not be guilty of more heinous crimes she has blurred the dates in her mind? Has she told herself this so many times that this has become her reality? Or has she, wittingly or unwittingly, over time given him an alibi?

'You can't find the photograph, but you are still very sure of what you've told me?'

'Oh, not this again!' she says, irritably. 'We've been over this so many times.'

'Yes, but there is still no proof, is there, that Derek couldn't have been in Adelaide?'

'Only what I'm telling you. And I don't tell lies.'

'I'm not suggesting you do. Elaine, Derek is a cricket fanatic. Can you ask him?'

'He can't take phone calls.'

'Can you write and ask him?'

'No. They vet his letters.'

'What does that matter, if it proves he couldn't have been in Adelaide? It would help prove these things, one way or another.'

'We want to let this rest!' Now Elaine has raised her voice slightly and I can hear she is exasperated with the constant questions. 'What good is it, bringing all this up again? My sons don't want this and neither do I. What good can come of it?'

'There are a lot of families out there looking for answers, either not knowing where their children are or not knowing who murdered them,' I tell her. 'It would be good if you could help, if you do know more.'

'Ernie might have known more,' she says. 'I don't.'

I remember what the police officer told me: Elaine conveniently hides behind her dead husband.

'Do you think you are in deep denial, Elaine, about what Derek has done?'

'Probably,' she answers. 'Probably.'

I am remembering, too, those ghastly crime scene photos and the hundreds of hours I have spent talking to and sometimes consoling victims' families; the hours I have spent crisscrossing the country, from Tasmania to Victoria, New South Wales, Queensland and South Australia, talking to police, lawyers and psychiatrists about Derek Percy; the time spent tracking down neighbours, childhood friends and naval colleagues. My patience is becoming frayed, too, though I try to keep in mind the lament of serial killer Geoffrey Dahmer's mother, Joyce, who, it was suggested, was somehow responsible for her son's aberrant criminal behaviour. 'They're still blaming mothers,' she sighed after his arrest.

'If you know anything at all, Elaine, please tell me.' I am pleading with her now and surprised to realise that I am close to tears. 'Please. There are so many families who are suffering.'

Elaine's retort is loud and clear. 'This has ruined our family, too! We just want to forget about it.'

'I understand you want to forget about it, just as I know the Tuohy family want to try and forget how their twelve-year-old daughter was murdered and mutilated. But they can't forget. None of these families can forget.' And in the brief, uncomfortable silence that follows I suddenly realise that even if Elaine Percy does know that her son is responsible for any other horrific child crimes, even if she does hold the key to it all, she does not want his name to further sully the family's reputation. What's done is done, and it can't be undone.

'There are grieving families out there, Elaine,' I repeat, failing to disguise my exasperation. 'They have a right to know what happened to their children. They have a right to some peace.'

'Well, I'm sorry for them,' she snaps. 'I really am. But I can only look to the future now, what future I have left. This whole business has ruined our family. We have a right to some peace, as well.'

There is no more to say.