We took the broomsticks back up the long shaft and back again into the light of day. The map showed no one near, and Harry had not yet received any sign that Riddle had heard. This was slightly disquieting, but the last Harry had seen, Riddle was overseas. We realized it might be some time before the news got to him.

We had now only to wait. The children decided that we might as well stay as we were, since no one would have any reason to come anywhere near this part of the castle at the moment.

But Sherlock Holmes clearly had no intention of waiting anywhere. Indeed his manner suddenly became quite brisk and animated as he informed Harry that there were one or two points he should like to clear up, and that he thought he could do so best by a brief investigation of a few things in the castle. No, he did not need any of the children to accompany him, but he would appreciate the loan of the map, since they were not likely to need it in here. It was a testament to the enormous confidence which they had come to have in my friend that they did not even state objections to this. Hermione thought it well to go over a few of the dangers again, but no one attempted to forbid or dissuade him. As he and I were leaving the room, Sherlock turned suddenly.

"If we are not back by the time Riddle has set out for Hogwarts, contact me."

The children glanced around at each other, and Harry hesitantly nodded.

"No really. I mean it, Harry. I've made you a number of promises over the course of this venture. I have done, and will do, my utmost to fulfil them. Now I'm asking one of you. When you hear from Riddle, I need to know."

"Is it really so important, Mr. Holmes?" asked Harry. "I mean, no offence meant, and I'm sure you can understand ..."

"Of course I do. And none taken. I can appreciate your concern. But it is very important. Do you promise?"

With some reluctance, Harry did.

Once out in the corridors again, and quite alone, I ventured the question of 'where' myself.

"We're going to call upon upon the headmaster." said Sherlock without breaking stride.

I stopped in surprise; then ran to catch up.

"Sherlock! We're burglars! We can't just go walking into the headmaster's office!"

"Did you bring the duct-tape?"

"Yes."

"Well, no worries then."

"Look, Sherlock, I know think there's more going on with Severus Snape than everybody else realizes. But you've told me yourself, he's a dangerous man!"

"Oh, I quite agree, very dangerous. But then I am too. And I have duct-tape."

"You are joking, right?"

"Just part of the way."

"Well, joking none of the way – why are we doing this? If this is about Harry, how will it help him?"

Sherlock turned around.

"Dumbledore must have left information with someone. He, understandably, did not leave it with Harry. So who would he have left it with? As far as I can tell, Kingsley Shacklebolt does not know. Lupin obviously has no clue. In fact, none of those Order members whom we have met seem to be in the slightest aware of any danger that area.

"Several things stood out to me in Harry's portrayal of Dumbledore's behaviour the night he was murdered. One, that after completely and absolutely trusting a man for years – defending him to Harry that very night – Dumbledore would quite suddenly, and with no evidence that I can discern, take the man's treachery so for granted that rather than expecting him to aid him, he pleaded with him for his life. And note: I don't gather that Dumbledore was generally the pleading type. Two, that when confronted by a murderous teenager he did not even attempt to defend himself. Three, he froze his companion, a reasonably competent Wizarding fighter, who could have helped to prevent the tragedy. There is also Professor Snape's own peculiar behaviour, but we've already gone over that."

"Yes, we have."

"Harry assumes that when Dumbledore said 'please' to Snape, he meant 'please don't kill me'. But Dumbledore did not actually say that. He said just 'please'. We do not know what it was that he was asking. Harry's assumption, though superficially obvious, seems to me to be highly unlikely. It would be uncharacteristic of Dumbledore as his history has been portrayed to me, and more importantly, it would be unnecessary. Dumbledore had no good reason to believe that he needed to so plead. It would therefore be reasonable to postulate that he might have been asking something else entirely, in which case he would have been referring back to a previous request, command, or conversation, and trusting Snape to know what it was that he was asking of him.

"The second two are closely intertwined. Harry seems to assume that Dumbledore lost to Draco Malfoy because he was too busy freezing Harry so as to protect him. This is nonsense. There was no one on the roof at that point besides Draco. Harry could, I am sure, have held his own against the other boy quite handily. Dumbledore could very easily have removed Draco from the equation entirely. Then both of them would have been ready to defend themselves against the others who came up. Freezing Harry did in fact protect him, true. But it was not the only thing which could have done so, nor the most effective if the object had been merely that. What it did do, was prevent Harry from interfering."

"Prevent Harry from keeping the Death Eaters from murdering him – Dumbledore?"

"Yes. ... Now, this faith Dumbledore had in Severus Snape – if we temporarily remove the fact that Snape killed him from the equation – seems to have been entirely justified. Snape, however unpleasant a person with however dark a background, did in fact come through for Dumbledore in all the cases that we can see. This last case could be the exception to the rule, true. But do we in fact have any evidence that it was? Dumbledore's behaviour does not suggest it. He let himself be disarmed and surrounded. He made sure that his fellow fighter could not interfere. And then he asked Snape to do something, something he knew that Snape did not want to do. Something he wasn't sure that Snape was willing to do, so unsure that he not only asked, but pleaded with him to do it. And Snape killed him. What if, John, what if, rather than spurning his commander's plea, Snape was in fact obeying him?"

"You think he was saying ... 'Severus, please shoot me.'"

"On the surface a preposterous theory. But let us apply it to these unmanageable facts, and see if it doesn't make any sense out of them. If Dumbledore planned on being killed by Snape that night, self-defence would not need to enter the question. He would merely need to prolong the interview with Draco until Snape himself could get there. This is exactly what he did. If being murdered was his plan, then not only would he need to hide Harry to prevent him from sharing the same fate, he would need to restrain him, to prevent him from kindly but unhelpfully trying to effect a rescue. If he had commanded a loyal follower to kill him, that follower might very well be reluctant to do so for a weighty plethora of reasons. He might be so reluctant that Dumbledore would be afraid that he was going to back out last minute. The situation would of course prevent a reiteration of the actualreasons, and Dumbledore might fall back on merely imploring him.

"Dumbledore seems to have known of Draco's plot to murder him – but as far as Harry could tell he did nothing about it. There is reason to believe that Dumbledore was terminally ill – it is at least certain that he was a centenarian with a wound that was refusing to heal. There is no reason to believe that he doubted Snape's loyalty, or that he had reason to doubt Snape's loyalty. It is also true that Dumbledore, knowing as he did the state of both the Wizarding government and the Death Eater movement, must have seen the likelihood of this exact state of affairs coming to pass. Dumbledore was the leader of the Order of the Phoenix, but he was also the headmaster of this school. If Riddle came to power, Hogwarts would be under Riddle's control. Dumbledore was – in great probability – already dying, or at least not far from death. Dead, he would not be able to continue his hunt for the horcruxes, or influence the conditions in his school. He bequeathed the horcrux hunt to Harry. And the school ... The trio are enraged, they cannot believe the injustice of the successor whom Riddle has chosen for their beloved headmaster. But they are wrong.

"Dumbledore chose the successor. He chose a man whom he trusted deeply, who has proved his ability to co-exist with the Death Eaters for long periods of time, who can be counted on to coldly choose between greater and lesser evils when no good choice is available, who has long had a foot in both Hogwarts and the Death Eater camp, and who, in spite of his reputedly unpleasant disposition, has demonstrated dedication to protecting the students of Hogwarts from actual harm. And he had this man murder him in front of witnesses from both sides. ... Morally questionable, no doubt, but really quite brilliant."

"Kind of hard on his chosen successor."

"Yes, it is. But you see how it all falls into place. Severus Snape's actions that night were not contradictory at all, merely deceptive."

"And you think that since Dumbledore divided his responsibilities between these two people, Harry and Snape, that he would have told whatever he knew about Harry's problem to Snape? That is it? That is your plan? To go for help to the nastiest professor in Hogwarts in the hope that Dumbledore gave him some last minute ploy to save Harry?" My heart had begun to sink.

"It's not a fool-proof plan, I grant you." said Sherlock, a bit uncomfortably. "And if you have any additional ideas, I would be very glad of it indeed. But it is the case that of the Order members in whom one would expect Dumbledore to repose confidences Snape was perhaps the least likely to be killed during Harry's hunt. The others would likely be fighting and scheming, and often on the run, with a great probability of being tracked down and murdered. Snape would be back at the school enjoying the favour of the new regime, as long as he continued playing his part cleverly – as he has done for years. If Dumbledore's confidence in him was comparable to his confidence in most of the others then there would be no one safer to leave vital information with. ... In any case, it would be criminal not to follow up such a lead. And as we are now nearing the headmaster's office, and there are persons relatively nearby, it would be well to end this discussion."

Sherlock had had the map open all this time; on its yellowed and crinkled surface I could see where the persons referred to were. We retreated out of the corridor into an empty classroom where the sun and air came in through curtainless casements and played upon the floor. Sherlock took what appeared to be a coil of peach twine and proceeded to thread under the door. In a few whispered words, he explained it was a Wizarding listening device which the twins had lent him. This would have appeared probable in any case, for once the majority of it was out in the corridor, he put the other end in his ear. That set up, he took from his pocket a small syringe. My alarm at the sight of this instrument in my friend's hands must have shown on my face. He chuckled silently at me.

"Relax, John." he said, and held up a small bottle. "A simple solution of veritaserum and a sedative. Perfectly harmless. And definitely not intended for me." He shuddered slightly as he began to fill the syringe.

"I see, so you don't intend to just take Snape's words to you as necessarily truthful."

"It is just as well to be careful."

"But mightn't the combining of the two interfere in the working of the veritaserum?"

"As if I would mix two solutions and just expect them to work! Really, John."

"On whom did you test it?"

"Remus Lupin."

"That wasn't very nice, Sherlock."

"Why, I assure you, revenge never even entered the question. I too completely approve of his actions for the matter to ever appear in that light. No, it was simply that because of our previous interaction on the subject, he seemed the appropriate person to ask for assistance. He very obligingly assisted me in both preparing and testing the solution."

The syringe full, he put a cap on the tip, and stowed it in his coat pocket. For several minutes we sat quietly in the empty classroom while Sherlock looked at the map and listened to the twins' device. His lips were parted slightly, and there was an eager look on his face. One of his fingers was anxiously tapping his knee. Then quite suddenly he wound up the twine and put it away. He took out his pistol and asked for the duct-tape. He then proceeded to thoroughly duct-tape his left hand to the gun, round and round and round, leaving nothing except his trigger finger free.

"See? Nothing particularly mysterious. It just occurs to me that this might prove somewhat effective against a disarming spell. You have your gun at the ready?"

"Yes. But, you don't sound as though you have any intention for us to use them."

"Of course I don't. We and he are allies. But whether we can get him to realize this or not is another question. Diplomatic procedures are sometimes more effective when both parties are armed. He certainly will be. Now, the coast is clear. Be on your toes."

Against one of the corridor walls, there stood a gargoyle, taller than a man, and exhibiting even more than the usual repulsiveness of its kind. I thought to walk on, but Sherlock stopped, and said a word which I did not catch to the statue.

It moved.

I leaped backward, stifling a cry of alarm. But my fear was unwarranted. It had merely hopped aside to let us pass. A door had split open in the wall, and a spiral escalator rose up before us. At the top of this we found a more ordinary door, a solid, fully visible oaken barrier, with a proper hinge, a knob, and a knocker. Without stopping to knock, Sherlock turned the knob, and strode straight in.

I gathered a general impression of a large and well proportioned room, big windows looking out on the green of the grounds and the blue of the loch, walls lined with paintings – portraits mostly, and shelves stacked with trinkets and books, but my attention focused immediately on the man who looked up from the desk as we came in.

It was a sharp, hard face, stuck in a scowl that looked as though it had become ingrained. His eyes were black and cold. His hair was black and hung in lank locks below his chin. He was dressed mono-chromatically in ample black robes, unrelieved by any lighter collar or cravat. The impression was simultaneously menacing and morose. I did not wonder that students hated him; he would certainly have been an object of fear and dislike to most children even if there had been nothing in his actual behaviour to justify it, so unpleasant was the effect. As we came in, his expression, which I should have been inclined to describe as impatient and bitter, changed in a flash to one of shock, and then of anger. Sherlock had begun talking the instant the door was open, crisply, clearly, and very quickly.

"Good Morning, Professor. I am here on a matter of business, of some import ... "

I would have been totally unsurprised if Professor Snape had refused to listen to a word Sherlock said. I would have been unsurprised if he had immediately gone on the attack. I would not even have been surprised if he had instantly summoned some of his Death Eater colleagues. What he actually did do surprised me very much.

He leapt abruptly to his feet and indignantly and imperiously demanded:

"What the devil are you doing here, Holmes?!"

Sherlock clearly hadn't expected this either.

"Oh." he said. "We've met then?"

Professor Snape rolled his eyes with a gesture of what might have been disgust.

"You won't be able to remember it." he said tersely, moving aside some papers and picking up his wand.

"It wouldn't have been on April the twenty-fourth, would it?" asked Sherlock pleasantly.

Snape looked up.

" ... No. ... I believe it was on April the twenty-third."

"Hmm. No, I think it must have been the twenty-fourth. But anyhow, that's lucky. There need be no introductions between us."

Snape had his wand in his hand now, and he turned to us in a sort of viciously business-like manner.

"You will tell me why you are here. You will tell me who else is with you. You will tell me how you got into the school. I will know if you are lying. And then you will leave immediately. If you are very quick indeed, you may get out with your lives. If you are careless, I shall not be able to intervene on your behalf, and will be saved the bother of tracking you down and obliviating you. And if I may offer you a piece of advice, Mr. Detective, you would be wise to stop sticking your nose into affairs which are none of your business and beyond your ability. I did not think that even your ill-judged curiosity would lead you into such depths of stupidity. I shall be very much surprised if this last ridiculous mistake of yours does not turn out to be a fatal one."

Quite unabashed at being thus addressed, Sherlock continued with his statement.

"I am here to speak to you about the task which Dumbledore left you regarding Harry Potter and his secret mission, and a message that I believe you are intended to convey to him."

Snape stared at Sherlock. His wand fell slowly to his side.

He sank back into his chair and silently regarded my friend for the space in which a child's nursery rhyme could be recited. Finally, he said:

"How much do you know?"

"Rather a great deal." said Sherlock. "I know that you have served Thomas Riddle but ill for many years. I know upon whose orders you really shot Dumbledore last June. I know you saved Harry Potter's life that night in defiance of Riddle's actual wishes. I know you avoided killing Order members when Harry was evacuated last month, and I suspect you even attempted to discreetly intervene on their behalf. I know you can still get into the Blacks' old house, and I know that you did so, somewhat over a week ago. I know at least a part of why you were there. And I know you took away at least two small items..."

Snape started violently, and stared at Sherlock, it was hard to discern whether it was anger or fear in his face.

"I can describe them." continued Sherlock. "But unless you require the assurance that I am telling the truth, I need not do so. I also know that it is no grave injustice that you are following Dumbledore as headmaster, but a very clever move on Dumbledore's part. And I think it highly likely that Dumbledore gave you a certain very important piece of information, regarding either something to be done to Harry Potter, or something to be delivered to him, at some point beforeRiddle's death. ... Riddle dies today. Harry needs that information."

Snape continued to sit there, staring at Sherlock as if he were some marvellous beast.

"Dumbledore clearly underestimated you, Holmes." he said. "He thought he had put an end to yourinterference back in April."

"Fortunately not. And, as a result, the war is almost won. If you do not speak or act today, this morning, you lose the chance to do so. Am I correct in saying that grave results will then ensue, Professor?"

After another pause, Snape said:

"I know who you are. Dumbledore used to keep current with the muggle news and had no difficulty recognizing you. I did not see anything particularly entrancing about running into an overly nosey muggle detective, but he was delighted, and it was with a rather absurd regret that he obliviated you. I now see that he did a horrendously insufficient job. ... But who is this?" He jerked his head in my direction.

"Dr. John Watson. If Dumbledore introduced me to you, then you may have heard of him."

"I believe he directly asked why some muggle healer wasn't with you."

"That would doubtless be John. Professor Snape, Dr. John Watson. John, Professor Severus Snape."

"Good Morning, Professor." I said, trying to sound coolly business-like, as though breaking into Wizarding offices was all in a day's work for us.

"Hmph." said Professor Snape. "So Potter has allowed the two of you to latch onto him. ... Is he here?"

"He is. We are waiting for Riddle. We are expecting him and his python at any time now. By which point, I – or rather Harry – needs to know that information."

"His python? ... Why are you expecting Nagini?"

"Because we think it likely he will be exceedingly anxious not to lose sight of her."

Snape stood up again and paced back and forth for a minute. After a moment he seemed to make a decision, and snatched up his wand from the desk. Sherlock's gun hand instantly swung up.

"I'd be careful where I pointed that, Professor." he said quietly. "Unfortunately our weapons have only one setting and I should hate to be forced to use it on you."

Snape rolled his cold black eyes. There was a slight twitch of his wand and the pistol went flying. Sherlock Holmes flew with it. Perhaps just from the jolt, the gun went off and hit the ceiling. In the instant that Sherlock was in the air, Snape turned towards me. My gun was in my hand, but I didn't fire. From the floor on the other side of the room, Sherlock called:

"Hold it!"

The pistol was again levelled at Snape.

"You cannot possibly incapacitate, obliviate, or other otherwise disable both us at the same time. I am sure that you are a sufficiently accomplished wizard to immolate the entire office should you so choose, but I know perfectly well that you're not going to do so. If you wish further assurance of the legitimacy of our errand, I understand from Harry that you are highly skilled at some form of mind reading."

Snape scoffed.

"Mind reading is a muggle term. Potter has never progressed beyond the most meagre grasp of legilemancy. It's not mind reading. The term gives no conception of the complex and subtle art of ..."

"Terms, complexities, arts, and irritating students aside ... You can read minds?"

" ... Yes."

"Then, do so."

"That was what I was doing."

"Then you should have informed us of your intentions. Drawing a weapon is generally considered an offensive move." Sherlock stood back up.

Snape turned towards him.

"That one is absolute plate glass." he said, with a nod in my direction. "He couldn't hide anything if he tried."

"Mm." said Sherlock. "I know."

This made me slightly indignant, for I could keep a secret as well as the next man. But then I noticed that something odd was going on. Sherlock and Snape were staring at each other with a singular intentness, as if a line had snapped from eye to eye. Neither moved. Neither spoke. They just stood, locked in each others gaze.

I do not how long this lasted, but it stopped abruptly. Snape turned away. He suddenly seemed immensely absorbed by something on the desk. Which his back still to us, he said:

"I do not know how you know it ... but you are correct."

"Correct about what precisely?!"

"Potter carries a piece of the Dark Lord within himself ... and the Dark Lord cannot be killed while Potter is alive."

"And nothing can be done about it?! Nothing at all? Are you sure Dumbledore didn't tell, or even suggest, something which could be attempted? Perhaps even something that has almost no chance of success. There has to be something!"

Snape faced him with a bitter sneer.

"You think everything can be fixed with the flick of a wand, Muggle?" he asked in a dangerous, low voice.

"Tell me what Dumbledore said!"

"I have."

"And that is it? He gave you no task to perform, no commands on the matter?"

"None save to inform the boy when his task is almost complete."

"Just that?"

"Just that."

Sherlock seemed to fall back, away from the desk. The morning's energy had gone out of his limbs, and he suddenly looked very very tired.

Snape stood, arms akimbo, glaring as if the whole thing was our fault. Then he said:

"And you, Muggle, I suppose you think you're going to do it?"

Sherlock nodded dumbly.

Snape turned back to the desk. He opened one of the drawers with a jolt and took out a small bottle. Then he held his wand to his temple. My first, bizarre, thought was that he was siphoning cobwebs out of his hair. But it was not so; the substance, whatever it was, was more like liquid than like thread. He transferred it to the bottle, which he then capped. He held it out to Sherlock.

"And this is?" asked Sherlock.

"A memory." said Snape. "It contains exactly what Dumbledore said to me."

"Ah." said Sherlock. "You don't trust a muggle to deliver the message properly?"

"Nor Potter to listen unless it is Dumbledore who is speaking." snapped Snape. "He never has listened!" He took a large stone bowl, cunningly engraved, from a shelf behind the desk, and shoved it at me. "I want this back."

I took it mutely, with no idea what it was for.

Snape looked as though he was about to shoo us from the room, but he stopped with a tiresome roll of his eyes, and picked his wand back up.

"I suppose I ought to accompany you..."

"Oh, no. That's not necessary." said Sherlock. "We're perfectly capable of navigating the castle, and can avoid the other wizards quite well."

After regarding him for a minute with an unconvinced eye, Snape put his wand back down with a clatter.

"One other thing, Professor." said Sherlock. "You wouldn't happen to know anything about the present whereabouts of your erstwhile colleague, Miss Charity Burbage, would you?"

Charity Burbage, the young woman who disappearance we had been investigating the day we met the trio – this was the mysterious school up north where she had worked.

Snape dropped his eyes.

"She is dead."

"Ah." said Sherlock reflectively. "I feared as much." He made as if to walk away. "We shall, in any case, see that she is avenged."

"One moment, Holmes." said Snape commandingly. From out of a cupboard, he drew a long, gleaming sword; there were red gems inlaid upon the pommel and the hand-guard.

"I don't know why, but Potter is supposed to have this." he said curtly, holding the hilt out to Sherlock.

Sherlock took it quietly, and looked at it. Sunlight flashed up and down the blade, and played off the strange pattern of delicate ripples in the steel. "Godric Gryffindor." he read aloud, looking at an inscription near the hilt. Stepping away from Snape, he gave it a swing, and then another one, trying out the feel of the weapon. "Slayer of basilisks." he said quietly. Then he tucked the sword, un-sheathed as it was, under his left arm (the one which held the duct-taped pistol), and looked back to Snape. "I believe that I probably do know."

"Good." said Snape resuming his seat. "Then take it and go."

Sherlock turned away. I went to follow, but Sherlock abruptly spun around, the little syringe in his hand. The clear solution streamed out and splashed Snape in the eyes. He leapt to his feet, roaring and sputtering, but almost immediately sank back down, as if his body had suddenly become too heavy to hold its own weight. Sherlock bent over him, the little bottle of silver stuff in his hand.

"Are you there, Professor?" he asked

"Yes." replied Snape, sounding half asleep.

"Then tell me again what is wrong with Harry."

"A piece of the dark lord is attached to him, connecting their minds, and preventing the dark lord from being killed."

"And Dumbledore told you that nothing could be done?"

"He said that Potter had to die. There is no way around that. It cannot be undone."

Sherlock held up the bottle.

"Is the memory stored in this completely legitimate and precisely what actually happened?"

"Yes."

Sherlock stood up.

"Excuse the indignity, Professor, but you'll agree I had to do that."

And without another word, he turned and strode from the room.

But I hesitated, a flutter of movement had caught my eye. On the desk, only half concealed under a piece of parchment which someone had knocked about, was an animate wizard's photograph. In the corner that was visible to me, a pair of white hands were held out to someone outside the photograph, and lock of red hair (it was that which had caught my attention) was swinging.

Professor Snape's eyes had drifted shut, and his breathing had become regular as the sedative took effect. I slipped the photograph out from under the parchment. Three of the sides were smooth, but the fourth was rough, as if it had been torn. It was an image of a very lovely young woman; there was a singular sweetness about her laughing face, and gracefulness in her movements as she held out her arms to the person who never quite entered the picture. But what chiefly transfixed me were her eyes. I knew them. Even in so small a photograph their particular vivid shade of green was unmistakable. They were Harry's eyes. This was Lily; she whom all spoke highly of, who for her son had cast the spell which foiled even the Dark Lord, she whom Severus Snape, the Death Eater, had loved; for whose sake he had forsaken his ambitions and laboured long with difficulty and great danger to continue her mission and bring her murderer down, for whose sake he had watched over and protected the boy who bore that hated name 'Potter' – the boy whose death warrant he had just been forced to sign.

I glanced from the beautiful photograph to the face of the unconscious wizard. He was scarcely older than I was, and yet he was an old man; a sad and bitter old man, inky locks notwithstanding. Even in sleep, the hard lines the years had etched into his face did not smooth.

I set the photograph back down, and arranged the parchment so that it was fully concealed. And I too left the room.