The next day Harry confided in both Ron and Hermione the task that Dumbledore had set him, though separately, for Hermione still refused to remain in Ron’s presence longer than it took to give him a contemptuous look.

Ron thought that Harry was unlikely to have any trouble with Slughorn at all.

‘He loves you,’ he said over breakfast, waving an airy forkful of fried egg. ‘Won’t refuse you anything, will he? Not his little Potions Prince. Just hang back after class this afternoon and ask him.’

Hermione, however, took a gloomier view.

‘He must be determined to hide what really happened if Dumbledore couldn’t get it out of him,’ she said in a low voice, as they stood in the deserted, snowy courtyard at break. ‘Horcruxes… Horcruxes… I’ve never even heard of them…’

‘You haven’t?’

Harry was disappointed; he had hoped that Hermione might have been able to give him a clue as to what Horcruxes were.

‘They must be really advanced Dark magic, or why would Voldemort have wanted to know about them? I think it’s going to be difficult to get the information, Harry, you’ll have to be very careful about how you approach Slughorn, think out a strategy…“

‘Ron reckons I should just hang back after Potions this afternoon…’

‘Oh, well, if Won-Won thinks that, you’d better do it,’ she said, flaring up at once. ‘After all, when has Won-Won’s judgement ever been faulty?’

‘Hermione, can’t you —’

‘No!’ she said angrily, and stormed away, leaving Harry alone and ankle-deep in snow.

Potions lessons were uncomfortable enough these days, seeing as Harry, Ron and Hermione had to share a desk. Today, Hermione moved her cauldron around the table so that she was close to Ernie, and ignored both Harry and Ron.

‘What’ve you done?’ Ron muttered to Harry, looking at Hermione’s haughty profile.

But before Harry could answer, Slughorn was calling for silence from the front of the room.

‘Settle down, settle down, please! Quickly, now, lots of work to get through this afternoon! Golpalott’s Third Law… who can tell me -? But Miss Granger can, of course!’

Hermione recited at top speed: ‘Golpalott’s-Third-Law— states-that-the-antidote-for-a-blended-poison-will-be-equal-to— more-than-the-sum-of-the-antidotes-for-each-of-the-separale— components.’

‘Precisely!’ beamed Slughorn. Ten points for Gryffindor! Now, if we accept Golpalott’s Third Law as true…“

Harry was going to have to take Slughorn’s word for it that Golpalott’s Third Law was true, because he had not understood any of it. Nobody apart from Hermione seemed to be following what Slughorn said next, either.

‘… which means, of course, that assuming we have achieved correct identification of the potion’s ingredients by Scarpin’s Revelaspell, our primary aim is not the relatively simple one of selecting antidotes to those ingredients in a of themselves, but to find that added component which will, by an almost alchemical process, transform these disparate elements -’

Ron was sitting beside Harry with his mouth half-open, doodling absently on his new copy of Advanced Potion-Making. Ron kept forgetting that he could no longer rely on Hermione to help him out of trouble when he failed to grasp what was going on.

‘… and so,’ finished Slughorn, ‘I want each of you to come and take one of these phials from my desk. You are to create an antidote for the poison within it before the end of the lesson. Good luck, and don’t forget your protective gloves!’

Hermione had left her stool and was halfway towards Siughorn’s desk before the rest of the class had realised it was time to move, and by the time Harry, Ron and Ernie returned to the table, she had already tipped the contents of her phial into her cauldron and was kindling a fire underneath it.

‘it’s a shame that the Prince won’t be able to help you much with this, Harry,’ she said brightly as she straightened up. ‘You have to understand the principles involved this time. No short cuts or cheats!’

Annoyed, Harry uncorked the poison he had taken from Siughorn’s desk, which was a garish shade of pink, tipped it into his cauldron and lit a fire underneath it. He did not have the faintest idea what he was supposed to do next. He glanced at Ron, who was now standing there looking rather gormless, having copied everything Harry had done.

‘You sure the Prince hasn’t got any tips?’ Ron muttered to Harry.

Harry pulled out his trusty copy of Advanced Potion-Making and turned to the chapter on Antidotes. There was Golpalott’s Third Law, stated word for word as Hermione had recited it, but not a single illuminating note in the Prince’s hand to explain what it meant. Apparently the Prince, like Hermione, had had no difficulty understanding it.

‘Nothing,’ said Harry gloomily.

Hermione was now waving her wand enthusiastically over her cauldron. Unfortunately, they could not copy the spell she was doing because she was now so good at non-verbal incantations that she did not need to say the words aloud. Ernie Macmillan, however, was muttering, ‘Specialis revelio!’ over his cauldron, which sounded impressive, so Harry and Ron hastened to imitate him.

It took Harry only five minutes to realise that his reputation as the best potion-maker in the class was crashing around his ears. Slughorn had peered hopefully into his cauldron on his first circuit of the dungeon, preparing to exclaim in delight as he usually did, and instead had withdrawn his head hastily, coughing, as the smell of bad eggs overwhelmed him. Hermione’s expression could not have been any smugger; she had loathed being out-performed in every Potions class. She was now decanting the mysteriously separated ingredients of her poison into ten different crystal phials. More to avoid watching this irritating sight than anything else, Harry bent over the Half-Blood Prince’s book and turned a few pages with unnecessary force.

And there it was, scrawled right across a long list of antidotes.

Just shove a bezoar down their throats.

Harry stared at these words for a moment. Hadn’t he once, long ago, heard of bezoars? Hadn’t Snape mentioned them in their first ever Potions lesson? ‘A stone taken from the stomach of a goat, which will protect from most poisons.’

It was not an answer to the Golpalott problem, and had Snape still been their teacher, Harry would not have dared do it, but this was a moment for desperate measures. He hastened towards the store cupboard and rummaged within it, pushing aside unicorn horns and tangles of dried herbs until he found, at the very back, a small card box on which had been scribbled the word ‘Bezoars’.

He opened the box just as Slughorn called, Two minutes left, everyone!‘ Inside were half a dozen shrivelled brown objects, looking more like dried-up kidneys than real stones. Harry seized one, put the box back in the cupboard and hurried back to his cauldron.

‘Time’s… UP!’ called Slughorn genially. ‘Well, let’s see how you’ve done! Blaise… what have you got for me?’

Slowly, Slughorn moved around the room, examining the various antidotes. Nobody had finished the task, although Hermione was trying to cram a few more ingredients into her bottle before Slughorn reached her. Ron had given up completely, and was merely trying to avoid breathing in the putrid fumes issuing from his cauldron. Harry stood there waiting, the bezoar clutched in a slightly sweaty hand.

Slughorn reached their table last. He sniffed Ernie’s potion and passed on to Ron’s with a grimace. He did not linger over Ron’s cauldron, but backed away swiftly, retching slightly.

‘And you, Harry,’ he said. ‘What have you got to show me?’

Harry held out his hand, the bezoar sitting on his palm.

Slughorn looked down at it for a full ten seconds. Harry wondered, for a moment, whether he was going to shout at him. Then he threw back his head and roared with laughter.

‘You’ve got a nerve, boy!’ he boomed, taking the bezoar and holding it up so that the class could see it. ‘Oh, you’re like your mother… well, I can’t fault you… a bezoar would certainly act as an antidote to all these potions!’

Hermione, who was sweaty-faced and had soot on her nose, looked livid. Her half-finished antidote, comprising fifty-two ingredients including a chunk of her own hair, bubbled sluggishly behind Slughorn, who had eyes for nobody but Harry.

‘And you thought of a bezoar all by yourself, did you, Harry?’ she asked through gritted teeth.

That’s the individual spirit a real potion-maker needs!‘ said Slughorn happily, before Harry could reply. ’Just like his mother, she had the same intuitive grasp of potion-making, it’s undoubtedly from Lily he gets it… yes, Harry, yes, if you’ve got a bezoar to hand, of course that would do the trick… although as they don’t work on everything, and are pretty rare, it’s still worth knowing how to mix antidotes…‘

The only person in the room looking angrier than Hermione was Malfoy, who, Harry was pleased to see, had spilled something that looked like cat sick over himself. Before either of them could express their fury that Harry had come top of the class by not doing any work, however, the bell rang.

Time to pack up!‘ said Slughorn. ’And an extra ten points to Gryffindor for sheer cheek!‘

Still chuckling, he waddled back to his desk at the front of the dungeon.

Harry dawdled behind, taking an inordinate amount of time to do up his bag. Neither Ron nor Hermione wished him luck as they left; both looked rather annoyed. At last Harry and Slughorn were the only two left in the room.

‘Come on, now, Harry, you’ll be late for your next lesson,’ said Slughorn affably, snapping the gold clasps shut on his dragonskin briefcase.

‘Sir,’ said Harry, reminding himself irresistibly of Voldemort, ‘I wanted to ask you something.’

‘Ask away, then, my dear boy, ask away…“

‘Sir, I wondered what you know about… about Horcruxes?’

Slughorn froze. His round face seemed to sink in upon itself. He licked his lips and said hoarsely, ‘What did you say?’ ‘I asked whether you know anything about Horcruxes, sir. You see -’

‘Dumbledore put you up to this,’ whispered Slughorn.

His voice had changed completely. It was not genial any more, but shocked, terrified. He fumbled in his breast pocket and pulled out a handkerchief, mopping his sweating brow.

‘Dumbledore’s shown you that — that memory,’ said Slughorn. ‘Well? Hasn’t he?’