In spite of hesitancy that had possessed him on the evening of the second of August, Mr. Sherlock Holmes had plunged into the task of tracking down Thomas Riddle's safeguards with an energy which I usually associated with moments of crisis. But then, perhaps no case so critical had ever been put into his hands. I knew, for I had seen, that he had been hired by several heads of state on businesses of 'international importance'. He had exposed the continent's largest crime-ring and dismantled its command structure. But never before, to my knowledge, had he attempted to reverse a military coup.

The urgency of the matter impressed me ever more deeply the further we got into it; the spate of murders, political and recreational (terrible phrase), the danger to life and liberty being faced by those wizards who (like Hermione Granger) were born of muggle parents, the fact that Wizarding interference in muggle affairs was a very real possibility if they stuck to their strengths of secrecy and mind-control, and the revolting situation that a portion of what should have been free England was under a tyranny, were all very immediate dangers. Every day mattered. Every day might be paid in blood.

Up till now Sherlock had been balancing his Wizarding investigations with his consulting work. Now everything but the Wizarding case was dropped. The rest could be picked up later. He had asked Hermione to investigate Riddle's history, but they did it together. The two of them poured over recent criminal histories – both Wizarding and muggle, and historical accounts of Wizarding events and sites, anything which Riddle, in his twisted, prideful view of the world, might have considered momentous.

Fred and George Weasley had gotten all but one of the ex-addresses of the Death Eaters which Sherlock had asked for through their father by the evening of the third of August – that of the Lestranges' house, which was currently unoccupied, and those of the Averys' and the Dolohovs', which had relatives living in them. They brought back a lengthy response to Hermione from Mr. Shacklebolt at the same time. This letter pleased Sherlock immensely, for it was wonderfully detailed. No impressions and half remembered notions. Lots of good hard facts with dates and addresses, presented with a thorough understanding of context. He seemed to recognize some of the cases, and I guessed that a few wild theories of his had just been vindicated.

The shop that the trio suspected, Borgin & Burke's, was searched through, twice. The first time in daylight under the guise of being ordinary customers doing some very in-depth window shopping. The second after closing time, which was even more in-depth. The ancient Lestrange mansion was scoured over. We visited several odd, out-of-the-way corners which Sherlock and Hermione thought had thought sufficiently important to merit investigation. We found nothing; no horcruxes, and no indications suggesting anywhere else they might be. The idea that the Lestranges had hidden one in Gringotts had grown on the children. And in view of the immense respect that the wizardshad for Gringotts, Sherlock seemed to be relaxing his 'too obvious' views a bit.

And Sherlock still – there was little enough time, I don't know how he managed it – was going through that terrible book Hermione had lent him at an alarming rate. He seemed to be carrying it around with him so that if he had a moment he would pull it out and read. My initial response of strong distaste towards the volume had increased into a kind of fear, though I don't suppose I had a clear reason. I happened to be standing right behind him once when he opened it. It was handwritten like a medieval manuscript; it may have actually been one. I wondered that the crumbling pages could still survive being turned. The hand was a hard one. The black lines were like assaults upon the paper. Somehow the very illumination of the capitals seemed an obscenity. I caught no full sentence in my brief glimpse, but I caught words.

A few days before I would have said that there was no such thing as witchcraft. When I met the three youths, I treated their strange vocabulary as merely an extremely odd way of referring to what was clearly just a strange form of technology; peculiar certainly, but quite innocent. And regarding the three, I still felt the same. The fact that they clearly believed themselves to posses innate abilities of some kind as well complicated the matter somewhat. But that inclusion in their secret society might be based on carrying a particular genetic trait, and that their technology might take advantage of that trait in some manner, was not unthinkable. All their illusions, teleportation, blasting rods, invisibility cloaks, and remarkable capabilities in matters of forming, shaping, and fixing matter seemed morally harmless. I could not see that the things which they were doing were in any way intrinsically evil; certainly not any way in which they could be connected to the demonic. It was a different technology – not too different in many ways from what I could see on the science-fiction channel.

But when it came to Riddle, I felt differently. Felt, true, not thought. But somehow I could not label him merely, as Sherlock had done, 'mad-scientist'. I could not look upon 'Secrets of the Darkest Art' – that hideous volume which gentle Hermione held in such utter abhorrence and which my friend was so voraciously studying – and think only that the science in it was being put to vile uses. It was not only more sinister, but a different kind of sinister. Strange that a contemporary terrorist and small-time dictator should have inspired such notions, but Riddle did. Strange that I, who have always considered myself to be a pragmatic, level-headed person, should have entertained them. But whatever the reality of the situation was, and though I shrank from putting it into words even to myself, Riddle had become, in my mind, a sorcerer, and 'Secrets of the Darkest Art' a book of – in the old, dark sense of the word – witchcraft. And I wanted Sherlock to get rid of it. I didn't directly say that, but I did ask him if it was really necessary to read it. Didn't we know enough to go on? "Ignorance does not know itself, John." he replied. "If I am overlooking a vital piece of information, I will overlook the the fact that I am overlooking it." And he didn't put the book down.

And he still didn't say what it was that had him worried about Harry Potter. Since his admission to me that he had some secret knowledge, not another word on the subject had crossed his lips. Several times I had thought that he was going to tell me. But then his mouth would close, his eyes would drop to the ground, and he would turn away. He would then either shut-up entirely, or begin talking very fast on an unrelated subject. From a confidence built of long experience, I trusted my friend to reveal this information at the right time, or to forever conceal it if it was better off concealed. But it bothered me. It bothered me greatly.

I myself had been alarmed by the severity of the pain in Harry's old wound. It had clearly been a bad injury and was an unusual case. I had asked Ron and Hermione about the scar on his brow.

"Gee, I keep forgetting you're a muggle and don't know stuff like that." Ron said. "I knew about that scar ever since I was little. That's where You-know-who's curse hit him."

I received from them a rather more lengthy and dramatic version of the tale of Harry's infant encounter with Riddle. His father James had died fighting valiantly, albeit fruitlessly. His mother's protective spell had been cast as she flung herself into the path of a 'curse' meant for Harry. The second curse had hit him, and according to all the rules, Harry should have died. Every single person hit by that curse had died instantly, every single one – except for Harry. Whatever it was that Lily had done, as she sacrificed her life for her son's, overrode the ordinary rules. The shot glanced off the infant's forehead leaving only that jagged red line behind. Apparently it had never been a real wound. It was even, in the ordinary sense, not a scar at all. It was a mark, the same on the day it was inflicted as it was sixteen years later. They called it the lightning scar.

Since the injury had been inflicted by a mechanism of which I was completely ignorant, causing symptoms which I had never seen before, I was hardly in a position to say anything particularly helpful on the subject. When Harry said that there wasn't anything to worry about, he was in a better position than I to say. But I didn't really believe him anyway. If nothing else, episodes of incapacitating pain such as I had witnessed were not only a problem in view of the personal suffering involved, but in view of the dangers of becoming suddenly incapacitated. If such a fit came over him while operating a motor vehicle, for instance, the results could be catastrophic. Moreover, pain is nature's warning signal; a sign of something dreadfully wrong.

I also knew that he was in very great danger of being taken by Death Eaters, or Wizarding government officials, or even just unscrupulous wizards hoping to earn a reward. 'Undesirable Number One' were the words on the wanted posters. I knew a very small mistake on his part could result in capture and an ugly death.

Yet neither of these real and pressing dangers to the boy seemed as though they could be what caused Sherlock Holmes to behave as he did. He had guessed at the danger Harry was facing before he'd ever seen his face. A chronic health problem, however unpleasant in itself, would certainly be considered of secondary importance at such a critical moment. And both of these were common knowledge.

I thought it strange that in this case – where he was being unwontedly liberal with information – I was disturbed in a way that I had never previously been about that which he was keeping hidden. For I never had seen Sherlock so open in his plans and his theories as he was now. He was of a very secretive nature, with a somewhat intemperate delight in the dramatic. It was his habit to never reveal his whole plan or everything that he knew or guessed to anyone, not even to me, until the denouement of a case. But in this instance he was not acting as a private detective, hired to get to the bottom of the matter on his own by his own methods. Rather, he had been reluctantly accepted into a group that was already acting upon the problem. The situation by its nature forced him to to act with them, telling them clearly what he knew and openly explaining his plans in full detail. It was strange to me, and a source of some entertainment, to see him sit about a kitchen table with the three teenagers, propounding his theories and strategies in such unmysterious entirety.

A total of three different expeditions were made to the house of Dolores Umbridge, the woman who'd taken the locket from Fletcher; four if you count the fact that Fred and George Weasley went and checked it out themselves just to make sure that it was indeed the correct address before they passed it on to us. While Hermione and Ron were in Diagon Alley, checking on the hidden camera (which revealed that Bellatrix Lestrange had been in and out of Gringotts bank not once but thrice since the coup), Sherlock, Harry, and I went on a reconnaissance mission. Then, later on in the day, the five of us went ahead and searched it.

There did not seem to be any alarm systems, and none of the neighbours were in a position to see our entry, so we got into the house safely without being seen or setting off any alarms at one o'clock in the afternoon, which left us plenty of time to examine the house at our leisure before Ms. Umbridge would return. But after several hours of fruitless search, we were forced to come to the conclusion that the big gold locket engraved with an S was not to be found at her home. We knew that it might well be on her person; it would be no strange thing for a woman to wear a necklace to work. But the nasty thought that it might have passed on to someone else occurred to us.

We returned that night. We waited in the garden while some late-night guests meandered away. Finally, some time after the last light had turned out and the house had clearly retired, Harry, Hermione, and Sherlock entered the house a second time, while Ron and I stayed in the garden to give the alarm should anyone show up. The plan was for them to quietly locate the locket, create a replica of it so Ms. Umbridge wouldn't realize it was gone (Hermione was very good at that sort of thing), and then leave without anybody ever realizing we'd been there. But either they triggered a night alarm of some kind, or Ms. Umbridge was still awake and listening. We heard cries and bangings from the upper floor. A moment later there was a noise rather like firecrackers, and from my vantage point among the pink peonies, off to the left of the porch, I saw a group of cloaked figures rush up the front walk.

"Six at the front door!" I hissed at Ron, who stood opposite the bedroom window.

The front door slammed with a bang. My orders had been merely to alert, and not to fight, but now that it was too late to do anything I felt as if I should have hindered their entrance in some way. I bolted round the side of the house to join Ron, who had just signalled the three upstairs.

Sherlock Holmes appeared at the window. For a moment I was confused, then I realized that he was tearing out the screen. For a moment the window was empty again. I thought I heard Sherlock's voice, lifted momentarily with impatience. Then Harry jumped over the sill, and was in the air. I saw the glitter of gold swinging from his fist. Then he was gone; teleported. Sherlock appeared again. He made a sweeping motion with his hand. The meaning was clear; 'Go'.

Ron grabbed my hand, but made no move to run or teleport. He stood stock still, staring up at the window. His hand was cold and sweaty in spite of the warmth of the night. I could not hear the sound of feet, but I knew the cloaked figures must be upstairs by now. I could see Sherlock, near the window. From his posture I thought his gun was drawn and trained on the door. Hermione was still invisible in the depths of the room. For several terrible seconds we waited, staring up at the window.

Sherlock vaulted over the sill and plummeted towards the hollyhocks.

I heard Ron hastily whisper something, but if it was an incantation to slow Sherlock's fall, I scarcely think there could have been time for it to have an effect. Fortunately, the window was but one story off the ground and it was ornamental grasses and soft earth below, besides which, Sherlock was somewhat skilled in matters of jumping. Hermione followed immediately behind him. They leapt to their feet in the garden. The bedroom above filled with a burst of red light and much crashing as the door came down. I saw them reach for each others' hands.

"Come on." said Ron, and twisted away from me. Just before the strange blackness of teleportation slammed down over I heard not one, but two cracks, almost simultaneously. There should have been only one, for Sherlock could not teleport himself. But I had no time to wonder at it, for we were being crushed, and twisted, and suffocated in the lightless limbo. It seemed worse than it had before. I felt as though I was being torn in two. Then, just when I thought I must break, we were out.

Strangely it was still dark and suffocating. There seemed to be a whole crowd of people squished onto the one top step. Ron and I would have been unsteady on our feet in any case. And the step just couldn't fit that many people. And so, predictably, we all lost our balance and tumbled down onto the side-walk, where we lay in a tangled pile of limbs and groans, and I vowed to myself that never ever again would I consent to teleport with Ronald Weasley.

Sherlock was already back on his feet, and I expected to hear him snap at Ron and me for not having gone when he told us to. (And I for one was perfectly prepared to agree with him.) But he did not. Instead, in a voice of mildly veiled sarcasm, he said:

"Good evening. Are you looking for something in particular? Or are you just sightseeing?"

I looked up. We had fallen outside the 'enchantment' boundary. Sherlock Holmes stood over us, his tall, spare form drawn up to its full height and his hand grasping something half out of his jacket pocket. Two men stood in the road-way, staring. The garish light of the street lamps turned the folds of their cloaks to orange, and painted their faces, marred in every lineament with scorn and vicious passions, a ghastly, inhuman hue. Evidently they had been taken by surprise by the suddenness and indignity of our entry out of thin air; otherwise they would have acted more quickly. Even as I saw them, their hands moved for the wands on their belts.

Sherlock's hand swung upwards in response. I struggled hastily to reach the pocket where I'd stowed my weapon.

"Expelliarmus!"

The men stumbled, clutching fruitlessly after weapons which had flown from their grasps. In the moment they looked away from him, Sherlock leaped forwards and caught the one on the side of the head with the butt of his pistol. The other fell, apparently due to a number of spells cast by the teens.

Harry walked out of the blue, their wands in his left hand.

"What happened?" he asked.

"We all tried to apparate onto the step at the same time." explained Hermione.

"What happened, up there?" I asked. "With Ms. Umbridge?"

"We had to stun her." said Hermione. "She'll be okay." (Ron snorted and mumbled something about 'sick' under his breath.) "She won't remember any of it tomorrow, and I got the replica done, so no one should know why we were there." She looked down at the unconscious men on the pavement.

"Are they Death Eaters?" I asked.

"Well, they were hanging out watching the house and were going to attack us, so yeah, probably." said Ron.

Sherlock bent down and pulled aside the right sleeve of one of the men.

"Ah, Sherlock, it would be on the left." Hermione said.

So he pulled aside the left sleeve. On the man's forearm was a large, ugly red scar. When I looked closer, I saw that it was a brand. An image of a skull and a snake had been burned into his skin.

"That's the dark mark." said Harry. "They are Death Eaters."

"Oh! What are we going to do with them?" said Hermione.

"Well, first things first." said Ron, and pulled something out of his pocket.

One of the street lights went out.

I thought nothing of it; street lamps sometimes did, especially in run-down neighbourhoods like this.

Then a second went out. A third.

I immediately jumped to what I still think was the very reasonable conclusion that the disappearing lights heralded the approach of some unknown menace.

"What is doing that?!" I cried, drawing my weapon.

"Oh! Sorry, that was me." said Ron, holding up the item he'd taken from his pocket. It looked like a small cigarette lighter. He clicked it. Light suddenly whooshed out of it and flew back into the street lamp; he clicked it again and the light disappeared.

"Well stop clicking it on and off." said Harry. "That sort of defeats the purpose."

"Oh. Right." Click. Click. Click. We were left in darkness.

"Lumos." A pale light glowed at the tip of Harry's wand. "We'll have to just obliviate them like we did Rowle and Dolohov."

"My offer does still stand." pointed out Sherlock.

"Yes, I know." said Harry. "But putting them in muggle custody is just asking for trouble."

"Then can I have those?" Sherlock indicated their wands, which were still clutched in Harry's left hand.

Harry handed them to him.

"What do want with them?"

"This."

And with a sudden movement, his knuckles turning white in the effort, he snapped them both in two.

"I'm not giving them back their weapons. Now, Harry, why did you go back?"

"Oh, that's what that noise was." said Ron.

"To make sure you all got away, of course!" said Harry.

"You shouldn't have done so unless we failed to appear within a reasonable time period. You were supposed to get the item safely away from there."

"I did! I didn't bring it back with me."

"Where is it now, then?"

When went back through the boundary, Creature was standing silhouetted against the lighted doorway, the locket hanging from his fist.

That it was indeed the right locket was in no doubt. Harry recognized it, and so did Creature. That it was still a horcrux, safeguarding Riddle's life, that it had not yet been destroyed, was easily ascertainable. Even I, holding the large, cold, golden ellipse in my hand, could tell that something was not quite normal about it, not quite right. And the more knowledgeable Hermione was quite certain of the fact.

Sherlock Holmes then inadvertently gained the shock and ire of the three by quite innocently asking them whether they could do the 'avada kedavra curse'. He knew only that it had been named in the book that Hermione had given him as something which would sometimes destroy horcruxes. But it turned out to be a forbidden spell among most decent wizards. It was a favourite weapon of the Death Eaters – the killing curse. It had left that mark on Harry's forehead. It was the curse which had struck down Amelia Bones – that deadly weapon which killed but left no trace, and left the police all in confusion.

Neither Sherlock nor I quite understood how the potential to be lethal made a weapon unusable. We were, after all, hunting these things down with the intention of killing a man. Whatever there was about it which made it more evil than a gun I did not learn. But the children would not hear of it being used. And, what made the point moot in this situation, they couldn't do it.

Then, clearly not content with merely shocking them, Sherlock also asked them to lend him the horcrux for the night. He wanted to see what muggle technology could tell us about it, and asked Harry if he could take it down to the lab, promising to bring it back by morning. Harry was extremely hesitant to agree to this. There was a brief flash where Harry's initial suspicion of Sherlock, and Sherlock's initial irritation with Harry – both surprisingly dormant for the past two days – seemed in danger of seriously flaring up again.

But the moment passed. Perhaps Harry remembered it was in part due to Sherlock that he had the locket in his hand at that moment anyway. Perhaps he felt ashamed of showing such open distrust of a companion who he had been given no reason to doubt and much reason to have confidence in. But he wiped the look off his face and turned to Sherlock with a great deal of reasonableness.

"All right. I suppose ... what you said earlier about two heads and two technologies ... it does make sense to see what muggle technology makes of a horcrux. I'll come with you."

Something about this speech seemed to strike Sherlock. It seemed to carry some meaning for him beyond what Harry obviously meant. But when he finally spoke it was merely to say, in perfect equanimity, that the proposed arrangement would suit him quite well.

He and Harry left, taking the locket and the invisibility cloak with them, and leaving a warning that they might not be back for some time. Ron and Hermione, though very happy, were yawning so much they were having a hard time seeing, and bade me good night almost immediately.

I followed their example, for the last several days had been long ones, and I was as weary as they. Like them, I was exhilarated by our capture of the horcrux. But the secret Sherlock was keeping concealed damped it somewhat. From his pause, I was certain that what Harry had said touched in some way upon it. But how could it? They were talking about horcruxes. And that couldn't relate to a secret about Harry – could it?

My inclination to instantly discount anything which would associate that youth and these abominable contraptions – which even if they were not, as the children said, made by black magic were at least stained with blood and crafted with evil intentions – was not the result of evidence, but of instinctual horror, and as such I knew it was not justified as an argument. And thinking about Sherlock's behaviour, it did seem to me that he was making some sort of an association between them. I thought of the strange way he had looked at Harry just now, while they were discussing the horcrux. I thought, ominously, of how he had at the start of our hunt asked Harry to be very careful in deciding to hunt horcruxes, of how he had asked him to choose between the hunt and his very life, to choose as if the choice was real. Could it be? Could some strange fate really tie Harry's life to the outcome of this bizarre gang-war?

But the thing was absurd. What connection could exist between them? And with this question, I remembered Hermione's exhortation to Harry about 'closing' a 'connection'. What connection? What if she had been speaking not metaphorically of mental coping techniques but of some literal connection? Had Sherlock discovered it? Or rather, what lay behind it, for he clearly seemed to believe that he knew something that no one else did, certainly that Harry did not know.

That was of course, the merest of accidental association of words. What had a 'connection' to do with a wound? A physical injury it was. Harry had collapsed in excruciating pain. I remembered the rigid agony of his muscles, the clenchings of his hands, and the graspings at his scarred brow. Whatever was wrong with him (and surely the initial injury must have been more severe than Ron painted it to cause such after-effects so many years later) it was a purely medical matter. It could not be that which caused my friend such disquiet.

But nevertheless, this 'connection' grew large in my imagination and weighed upon my heart; some unspeakable darkness which connected a big-hearted, conscientious, dutiful young man to the vile devices of a black-hearted murderer.

I took a cab, and in a short while was sitting at my own table, with a late night cup of tea in my hands. Mary sat across from me, wrapped in her dressing gown. It was two-thirty in morning, but my hours had been very irregular since Sherlock and I joined up with Harry, Ron, and Hermione. Mary had awoken at my return ... I wondered if she had really been sleeping at all. She did not look it. I reflected on the fact that this situation must be wearing on her. She was well used to there being details of Sherlock's cases which I could not, in honour and decency, reveal to her. But she was quite unused to me being absent at all hours for days on end, with no explanation given as to my whereabouts or occupation. No reproachful word had passed her lips on that score. And though she frequently questioned me, as though to see how far the ban of secrecy went, she never urged me to break my word to the unknown allies. But she would have been more than woman, or much much less, to maintain complete composure under these circumstances and not suffer greatly from anxiety and curiosity. And I for my part was sorry that I could share nothing of our doings and adventures with her, for my sake as well as her own. I would have greatly liked to hear what she might have to say on the matter. Her quick intuition might possibly see what lay behind Sherlock's behaviour; perhaps not set my fears at rest, but, like Sherlock himself, shed a light on what was so dark to me. But I kept my word, and more than the table intervened between us.

"I wish I knew what holds you so silent and melancholy, John." she said, echoing my inmost thoughts. "Is the case going badly?"

"No." I said, reflecting on the locket which was doubtless undergoing some theoretically destructive procedure that very moment. "I think it's going very well."

"But?" she said.

"Well ... Sherlock never actually tells me everything that's going on."

"Of course he doesn't, dear. He is Sherlock. Since when is that news? ... And since when has it really bothered you?"

I shrugged.

"You've been curious about his secret researches for months now. Curious – but not disturbed. If it was merely that Sherlock was being Sherlock and keeping secrets, then you wouldn't be worried about it one bit. What's different?"

I sighed. "Well ... I've never before got the idea that he was keeping a secret, not because he was still trying to form a theory, not because discretion required it, not because he was being dramatic, but because ..." I broke off.

" ... Because he's frightened?" asked Mary quietly.

I looked up in surprise. "What? No. No, no no. More like ... deeply concerned."

"Well that doesn't sound so unreasonable, or even unusual. He deals in serious matters. It's more than that."

"Yes, he's disturbed. He is disturbed."

"And you've no idea by what? ... You can't tell me?"

"No. I can't. ... I don't really know myself anyway. But, Mary ..." She was the best nurse I had ever known. My medical degree was higher than hers. My knowledge may have been greater. But her instinct was almost always right. And none other had a touch like hers.

But I could not think of how to state the problem without infringing upon the secrets. And I recalled that Harry's scar was said to be famous among the wizards. Mere mention of his scar might be enough to identify him, and that we were working with him was one of the things we had to keep secret. I could say nothing.

She reached across the table, and laid her hand on mine. Warmth seemed to seep from it through my limbs and mind. Under her sweet gaze – there was such clear and sparkling radiance in the blue depths of her eyes – the turmoil of my imagination calmed somewhat.

"Go to sleep, John. You'll want to be back at work on this tomorrow. Sleep."