Two weeks later, Tom was lying in his dormitory at Hogwarts: staring at flagstones between the Persian rugs. The excitement of buying his first proper home, had been spoiled by the cryptic message; someone was watching him. If asked, Tom would say nothing could get to him, but that clearly wasn't true. The message bothered him a great deal and even worse, someone knew it would.

Tom could be amused by something, then he'd remember and his smile would fade. The constant threat was sapping his enthusiasm and made him feel old. He touched the patch of scaled skin under his shirt; although the patch had not grown, it throbbed and kept him awake at night. Combined with the menace of some unknown tormentor, he felt himself sinking to a darker place.

'You've a black dog on your back,' the matron at Wool's said, when boys were out of sorts. Tom was tired throughout the day and his lungs only half inflated if he took a deep breath. When dealing with the unknown, everyone was a potential threat; it exhausted him and he had no idea who to turn to.

'Tom.'

Gary was at the door.

'They're letting us out after prep, with it being light; summer term privilege, I'm told. Coming?'

He wanted to say no and just lie on his bed, moping, but Tom forced himself upright.

'All right.'

They walked down the grass slope towards the quidditch pitch and Gary's purpose became clear. A group of eight or nine girls, were circling the edge of the forest.

'Evening ladies.' Gary smiled and nodded; far too confident for his own good.

They smiled briefly, out of politeness, but had no intention of making conversation easy for him.

'Tom and I were just enjoying the evening air, when I said: shall we see what the girls did on their holidays?'

'What did Tom say?' Vivian asked, hands finding her hips.

Gary shrugged. 'He didn't say much as it happens. Which, knowing Tom, I took to mean: let's go over and ask them.'

'I was in London. Seeing shows, riding the subway, catching rays in Hyde Park. You?'

'Oh, much the same, Vivian, but in Didsbury.'

She shook her head and turned to Tom. 'Did you miss us over the vacation?'

'Miss who?'Tom asked, his attention elsewhere.

'Us,' Vivian indicated herself, Eudora and Betty, 'your muggle studies classmates.'

The girls were watching him.

'Of course, who doesn't miss muggle studies?'

It was very like Tom to answer a question, with a question. Was he being gently sarcastic; did he genuinely miss them, or did he just miss the subject? They would probably never know.

Returning to the school buildings, Gary headed to the common room, but Tom peeled off towards the library, saying he'd catch up later. Betty looked pleased to see him and Tom felt a flash of sunlight, but not enough to banish the dark clouds. Someone like Betty could take their pick and probably would, so why should he care what she thought about him?

He did care though. He cared what Gary and Kit thought, what Betty felt and he cared that someone was watching him. Then, without warning, he saw the whole picture. This person remained nameless to confuse and isolate him; deliberately, so he would mistrust and suspect his friends. Divide and conquer. They genuinely were his friends — he knew that for certain — so the dark clouds gradually began to part

Tom was in his dorm for lights-out and the headcount, then he returned to the library. Always methodical in his approach, he searched, analysed, then tested rigorously; rejecting or making additions to what he considered proven fact. Tom could endure long periods of boredom between breakthroughs and needed no encouragement to keep going. The Map of the Mind was a work of riddles and half-truths. Bel Awil-ili was an irritating man: always talking about some map, but never mentioning where to find it. Riddling about its purpose, without drawing conclusions; hinting at powerful magic, then never referring to spells by name. His personality was mischievous and teasing; someone who delighted in frustrating others. Tom sighed and continued: just ten more pages before bed.

On Friday night, Tom was back in his regular section of the library. Eyes itching from a lack of sleep, but steely with determination. The Map of the Mind would help him find the chamber and the chamber would tell him who he was. If he knew who he was, the reason for his terrifying dreams might be revealed; then he could treat his condition before the scales spread. It was an interconnected chain, which needed to be solved one link at a time.

Tom was familiar with Bel Awil-ili now. A man obsessed with collecting dark arts from the four corners of the Babylonian Empire, then using them to influence its dynasty kings. They came and went, but he — Bel Awil-ili — would remain as a guiding light. The puppeteer, to a succession of puppet rulers. Tom hated the man for being so elusive, but admired his ambition. He attacked where the weak hesitated; however, this ultimately brought about his downfall.

Bel Awil-ili had summoned the Rabisu: a terrifying demon. The weak would rather fall on their sword, than look into its hideous eye. Inspired by early success, Bel Awil-ili's protégé — Nebuchadnezzar — rose to become the mightiest ruler of the ancient world. It was overconfidence which consumed this pair of great and feared men. Inspired by the Song of Gilgamesh, where Gilgamesh befriended the wild man, Enkidu; Bel Awil-ili romantically imagined that the Rabisu and he would form a powerful alliance. So the Rabisu was unleashed, but its intellect was far greater than either suspected. It had three desires: destruction, death and decay; which it directed towards Bel Awil-ili, closely followed by Nebuchadnezzar. The king whose empire crumbled to dust, after only a generation.

At 3am and in desperate need of sleep, the tiredness lifted from Tom's eyes. An ancient, Akkadian book of magic, continued the story where none had before. Bel Awil-ili was consumed by a former lover, literally. Paralysed, except for his swollen eyes, he was devoured alive, one piece at a time. A stark warning then followed: using The Map of the Mind, would awaken the Rabisu. Once awake, it would not depart until the death debt was paid in full. The final words were chilling: your last action will be to underestimate the Rabisu, a being in existence since the Enuma Elish, or birth of our world. Possessing the greater intellect of any scholar, with intelligence only exceeded by its profound cruelty.

Back in bed, Tom thought he would fall asleep instantly, but that was just wishful thinking. What should he do? Accept the risk, discover his identity and eliminate his note-writing tormentor; or bury the idea and take a safer path in life?

On reflection, that was likely to be a much shorter life too. He already knew his answer, the instant he'd read the first warnings.

* * * * *

Tom wandered down to the boathouse to think. Throwing stones into the water was calming; especially when his lack of progress threatened to overwhelm him. The antidote was to retreat and perform a simple, repetitive activity, which allowed his mind to wander. Hand-sized stones, lobbed into the loch from the jetty, always felt satisfying. He imagined their downward progress: escaping sunlight and embracing the chilly depths in slow motion. Standing beside Hogwarts' boathouse reminded him of early trips to the river beach at Tower Bridge, although the two locations could hardly be more different. Water created an open space without obstacles; it deadened sound and reflected a bigger sky. If he felt trapped or hemmed in, water offered a way out.

He didn't hear anyone coming down the stone stairs. Gary was concerned for his friend; Tom was tired all the time, rarely seen and permanently holed up in the library. Doing what exactly? No one knew and several friends asked Gary why Tom roamed the castle at night. Teachers were unaware of what Tom was up to, but the rumour mill at Hogwarts was constantly grinding away. Secrets rarely remained secrets for long, though pupils never passed information to well-meaning teachers. They lived in their world and the students lived in theirs.

'You know where the fun's at.' Gary interrupted Tom's daydreaming and gathered several stones, before joining him beside the loch.

Anyone else and Tom would have made his excuses, but Gary left private matters undisturbed. Time healed all was a favourite phrase of his grandfather's.

'You want to know what I've been doing at night.' Tom didn't look round.

'In one,' Gary skimmed a stone unsuccessfully.

Tom wanted to tell someone and Gary was the only real choice.

'I've found something. Something which might tell me who I am and where I'm from. Why performing magic is as easy as falling asleep.'

'I could help you know. Not in the book-learning department perhaps, but in other ways. That's what friends are for.'

Tom recounted what he'd learned so far. The Chamber of Secrets, The Map of the Mind and Bel Awil-ili's dark magic. How he was sure The Map of the Mind book was a key, despite it never explaining how to find The Chamber of Secrets. The Rabisu, he decided not to mention. Though he did leave a hint that using sophisticated dark magic, might have consequences.

'Stop me if I'm wrong, Tom, but this sounds bloody dangerous.' Gary lobbed a shot-put sized stone, which broke the surface with a satisfying thunk.

'Don't think I don't know it. You have to understand: I don't have a history; I just exist. No grandfathers; uncles; aunts; neighbourhood or birthplace. I know a small area of London's south docks and an even smaller area of Scotland. My birthday is the day I was brought to Wool's; no one knows when I was born, or where and information about my parents is non-existent. Today, at this moment; I'm barely here. Really, what do I have to lose?'

'You say stuff, like there's no choice but to agree. I can see your point, but you do exist. More than you know. You just need reminding from time to time, is all.'

Gary might not be Hogwarts' most academic pupil, but he understood people better than anyone else in their year.

Gary had become friendly with the Scottish caretaker at Hogwarts, since their midnight encounter last winter. Hubert Feather was eccentric, rather than unusual, but pupils still avoided him. Being short, with a weather-beaten face and confused expression, was enough for most to give him a wide berth, but he was actually a sensitive man, prone to bouts of loneliness and soul searching. Despite qualifying for access to the staff room at Hogwarts, few on the teaching staff spoke to him. It always felt like he was intruding on their personal space; so he rarely visited — except in the holidays — when few were around. Gary spoke to him regularly and discovered that he knew more about Hogwarts Castle, than any of the teachers. He tolerated the loneliness of his job, because he loved the buildings and their unique atmosphere. Feather often wandered the corridors at night, not to catch pupils out of bed, but to appreciate and savour the Gothic architecture.

Taking a considerable risk, Gary mentioned The Chamber of Secrets. Feather simply treated it as a conversational peg, to hang several opinions on. He explained how Salazar Slytherin had constructed the chamber when the school was founded, but everyone at Hogwarts knew that. He did eventually share some valuable information: revealing that there was a rumoured hidden entrance. Unearthed, then sealed when the bathroom plumbing was installed, several centuries earlier. Many at the time believed the chamber was still accessible and that one day, Salazar Slytherin's heir would discover it.

'Some say forces unknown have accessed the chamber ever since. Aye, it could be true that the plumbing concealed the entrance, by hiding it in plain sight. If you catch my drift?' Up by the second floor lavatory perhaps, who knows?'

'Have you seen it?' Gary asked.

'Ach no, but I've no' been looking. Anyway sir, I've got lamps below that won't bewitch themselves. Have a pleasant morning.'

'You too.' Gary was excited; Tom would have to be impressed by this nugget of information, wouldn't he?

That evening after prep, when they were supposed to be in the common room, or taking a breath of fresh air; Gary and Tom visited the second-floor girls' lavatory. At seven-forty-five in the evening, it was unlikely they would find anyone in there, but you never knew. People had an irritating habit of doing exactly what you weren't expecting. So they stood outside the door for several minutes: trying to establish whether anyone was inside.

Tom eventually swung the door back. The room was empty so they split up, scouring for clues; the longer they stayed, the greater their chance of discovery, so both moved quickly. Gary was thinking about breakfast, because he needed to concentrate on something and still didn't have a clue what they were looking for. After covering all the obvious places, they found nothing unusual.

Half-past eight was fast approaching and the chance of someone walking in on them, was increasing by the minute, so they closed the door and slipped along the corridor. It was only a short trip back to Slytherin House and no one was likely to notice their absence. Rounding the corner, they narrowly avoided walking into a teacher.

Professor Dumbledore looked them up and down carefully, only moving his eyes. Gary appeared relieved, but Tom was nervous. He'd managed to avoid any one-to-one contact with him since joining the school, but knew that eventually, their paths would cross. Why, of all the opportunities available, did it have to be this one?

'Good evening Mr Box. And to you, Mr Riddle. Taking a turn around the grounds?'

'Yes,' Tom replied, which made Dumbledore smile.

'An excellent decision on such a fine evening,' Dumbledore turned to Gary. 'How's the transfiguration assignment coming along, Gary?'

'Not quite done yet, but getting there, professor.'

'Good, good.' Dumbledore paused and made eye contact with Tom. 'A shame you decided not to join us, Tom, I hear you're a man of many talents.'

'Muggle studies was my preferred choice, sir.'

Dumbledore smiled again and nodded.

'Good evening, gentlemen.'

Dumbledore walked between them with his hands clasped behind his back. Gary pulled a face which suggested they'd had a lucky escape, but Tom didn't see it that way at all. He was unsettled by the encounter. Was Dumbledore the author of the note? Perhaps not, but for now he was still on the shortlist.

* * * * *

Transfiguration class in the summer term was on Thursday afternoon, between two and four. Difficulties in scheduling meant a double period was unavoidable, so well fed after lunch and with the weather improving, drowsiness had taken control of Gary's mind and body.

It was theory of transfiguration first, before they moved onto a practical exercise in the second hour. The class was attempting to turn a ladybird into a button and back again; turning something alive, into something also alive, was still years away for first formers. The prospect of changing an insect into a dull object like a button, wasn't helping. Gary's attention had drifted and with eyelids fluttering like butterfly wings, the urge to let his head drop was overpowering. Lunch had been hotpot with a sage-scone crust; hearty and filling, but that hadn't stopped Gary getting hold of an extra portion from a hotpot hater. On the verge of sleep, he had a flash of inspiration.

His eyes opened and locked on Dumbledore. Transfiguration was about changing one thing, into another thing, wasn't it? What if The Map of the Mind was just a type of transfiguration? It only appeared when...? When it was in the right place? The Chamber of Secrets, or somewhere else, who knew? Maybe it was the book after all; otherwise how would you find the chamber? Gary's scalp bristled with excitement and possibilities. He had no idea where the revelation had come from; whether the book would transfigure into the map, or where it had to be taken, but surely this was a breakthrough? He endured a miserable ninety minutes pretending to listen, while twitching in his seat. The practical was a disaster; Gary's ladybird ended up as three spotty buttons. When they were finally let out, he sprinted across the stone bridge to Slytherin; Tom wasn't there, so he ran over to the school library.

When Gary eventually found Tom, he explained his theory patiently.

'The way I look at it, the entrance only appears when the right thing is in the right place. Though obviously, I don't know where that is. Or what needs taking. The book is all I could come up with.'

Tom was still thinking things through; Gary could be right. The Map of the Mind book was certainly possible. Tom reviewed the text in his head: the more you looked, the harder it becomes to see. True, if the object was right in front of you and typical of Bel Awil-ili's riddling personality.

'You're a genius, Gary.' Tom could hardly believe it. His friend had solved a problem he'd been wrestling with for weeks. Here was an example of what could be achieved, when you had people working alongside you.

'I do try, young man.' Gary dusted off his shoulders.

Tom beckoned Gary through his portal and into the restricted section of the library. He took The Map of the Mind down from its shelf and showed Gary a coiled-chain mark on the binding.

'Not to be removed from the library. Why? So there's no danger of it accidentally transfiguring, when you wander around Hogwarts.'

'Can we not drop it out the window?' Gary looked hopeful.

'No. Most books in here can be moved, but not this one. The charm's powerful and could take years to crack. If Hogwarts crumbled to the ground, this book would still be here. The Map of the Mind is translated from Aramaic and before that, Akkadian; it's possible that was the language used to create the charm? No one knows.'

The brief high of Gary's discovery, was replaced by deflation and a feeling that the adventure into Tom's past had stalled. The magic was beyond Tom and the history: too patchy to make further progress. Neither said a word as they returned to Slytherin, but Gary felt he'd let Tom down in the search for his family.

Arching his back in bed, Tom kicked away his blankets while still asleep. Heat was pouring off him as he writhed between the sheets.

Deep within Hogwarts, he was standing before a sturdy door. Tom crashed his shoulder into the enchanted metal, but it was cold and unyielding. So dense, that no sound came from beating against it. He held his bruised shoulder with one hand. 'Open,' he pleaded. 'Open for me.'