Tension was high after the strange incidents. The Order of the Phoenix had convened to discuss how the Death Eaters could have gained entrance to the school, but their suggestions had yielded no practical possibilities.

Snape had only known that the Death Eaters were plannng to infiltrate the school and play tricks; he had never believed they could actually do it, and had certainly never expected one to be played on him. He had no idea how they had done it, and wondered why they had not contacted him beforehand, as he could have made their job easier by letting them into the school. Lord Voldemort was clearly keeping him out of it.

Confidentiality was of the essence. Albus Dumbledore managed to disperse the Dark Mark from the sky before the press or the Ministry caught wind of it, so that part of the situation was not made public. Only Professor Sprout and her class of Gryffindors had actually witnessed the Dark Mark, and since Death Eaters could easily break Secrecy Spells, Dumbledore was forced to magically remove that segment of their memories, so that after running from the greenhouse and standing outside, they remembered only being herded into the Great Hall with the rest of the students.

The excision of the Dark Mark from the events ensured that only the Order of the Phoenix would know who had done the magic; otherwise it simply looked like pranks by expert and slightly sadistic students. This, however, created feelings of hostility and distrust between all the students, especially against Slytherin house, reputed and even boastful of its brutal exploits. It was worse than the inter-house tension during the Triwizard Tournament the year before; skirmishes broke out frequently, of great and small magnitude, and at a major one of these Harry happened to play a key part, though not as a combatant.

One afternoon after classes, Harry and Hermione were walking through the Great Hall on their way to the library when a Hufflepuff second-year suddenly skidded round the corner and collided with Harry. She spotted Hermione's prefect badge and gave a gasp of relief.

"A prefect! Please, you've got to come-there's about to be a fight upstairs-"

The second-year led them upstairs and down a wide corridor, where a throng of young students were blocking the way. The students were gathered round two boys who faced off, wands raised.

"How dare you insult my parents!" bellowed one of the boys, a third-year Ravenclaw named Quentin Madley.

"They're Muggles, filthy Muggle lovers!" taunted Quentin's opponent, a Slytherin second-year called Malcolm Baddock. "What are you going to do, you Mudblood-"

Malcolm never finished, because Quentin gave a scream of rage and half the students fired curses at once. The area became shrouded in smoke and the din from the spells was deafening, covering up the sound of Hermione's shrieking, "Stop! Stop!"

The air cleared, but the students were still making a furious racket. Hermione pulled out her wand and shot white sparks over the crowd.

"Quiet!" she shouted. The students fell silent. Hermione pushed her way to the duellers in the centre of the assembly, yelling as she shoved people aside. "Put away your wands! If I spot a wand, the one holding it will be suspended!"

All the students hid their wands. Hermione reached the two boys and screamed. Harry, following her, could not contain a gasp.

Quent Madley sat on the floor, dazed from the explosions but unscathed. Malcolm Baddock, lying nearby, was not so lucky. Since the students who'd shot him were all novices, their hexes had been for the most part ineffective; but they had managed to seal his lips shut, give him onions for ears, put various boils, needles, and tentacles on his face, and make his legs jerked crazily in a quickstep. He stared at Hermione, the panic clear in his eyes.

Hermione rushed forward and tapped him with her wand. "Finite Incantatem!" she cried. His legs stopped moving and his onions became ears again, but no other change was apparent. Then Malcolm pointed at his throat and made muffled noises. He was clearly having difficulty breathing.

"He's choking! Do something!" a hysterical Slytherin cried at Hermione.

"Let me think!" Hermione snapped. She wrung her hands. "Let's see."

She tried a number of countercurses, but nothing worked. Malcolm's gaze followed her piteously, beseeching. His face was turning red.

Hermione jumped away from him, ashen. "I have to get Professor McGonagall!"

"I'll go," Harry said.

Hermione looked at him as if seeing him for the first time. "Harry! You know a lot about Potions!" She grabbed a Ravenclaw girl. "Orla, go fetch a teacher!" The girl ran off and Hermione turned back to Harry. "You remember what Snuffles said about Professor Figg? She published a paper about using potions to counteract curses."

"I read that paper last week," said Harry, realizing what she wanted. "You want me to try? But I don't really remember much."

"But Harry, I don't even know anything about that," Hermione said desperately. "I never read her paper. I study mostly Transfiguration. Please, you've got to try."

Harry knew that. He nodded, knelt by Malcolm, and started pulling his Potions equipment out of his bag. Improvising, he fireproofed his hat to use for a cauldron and started a fire underneath.

"If I can unglue his mouth I can see what spell closed his throat," he thought to himself. In his schoolbag he found a tube of potent Bundimun secretion, one of whose properties was a corrosive potency that made it a key ingredient in cleaning solutions. Harry dipped the handle of a knife in the tube, held it over Malcolm's face, and paused. "This will hurt a lot, but don't scream," he said to Malcolm, and then painted a thin line of the Bundimun's acidic liquid on the Malcolm's face.

The boy's lips parted, to Harry's relief. Malcolm tried to draw breath and failed. But when the boy opened his mouth Harry saw that he seemed to have swallowed an Engorging Spell that had caused the walls of his throat to expand.

"I can try a Deflating Draught," he said dubiously. He would have to be halve the measurement of Erumpent fluid or he could irreparably damage Malcolm's vocal cords. Though considering what he had just said to Quentin Madley, Harry thought, perhaps permanently silencing the Slytherin boy wouldn't be such a bad idea.

He assembled the ingredients quickly, his hands trembling as he measured out leech juice. When it was finished he tipped the steaming concoction down Malcolm's gullet. It sizzled and seared as it went down- but it did the job. Malcolm was finally able to wheeze in some air. He coughed and gasped, clutching his scalded throat, but he was breathing.

"You did it, Harry!" cried Hermione, dropping to her knees by the coughing Malcolm. Harry sat back on his haunches, feeling as if a great burden had fallen off his shoulders. Malcolm looked at him. "Thank you," he croaked feebly, rubbing his throat.

Harry nodded, not knowing what to say.

There was a commotion at the edge of the crowd as Harry applied an unguent of his own creation, a mixture of boil medicine and undiluted Bubotubor pus, to Malcolm's various facial growths. Looking up, Harry felt a nervous, sinking feeling in his stomach as Severus Snape shoved two students aside and reached the centre of the circle. All the students were silent immediately, fearful of this imposing man.

"What," he said icily, "happened here?" His frosty gaze took in flustered Hermione, white-faced Harry, gasping Malcolm, and the mess of Potions equipment strewn across the floor.

Hermione leaped to her feet. "Professor Snape, Malcolm Baddock and-"

"Silence, Miss Granger!" thundered Snape, but she was in a position of some right now, and was determined to exercise her power.

"I'm a school prefect, Professor!" she said, pointing at her badge. Snape blinked and frowned at it.

"So you are, God save us," he said, scowling at Hermione, and when she refused to quail under his gaze he let her be. "Then you will enlighten me, in a calm, truthful, and impartial manner, as to what occurred here."

Hermione related the story of the argument between Baddock and Madley, including the word employed by Malcolm at the height of the hostilities; at which point Snape regarded Malcolm with a cold eye, normally reserved for students of other houses. "Is Miss Granger's claim true, Mr. Baddock? Did you use the word 'Mudblood' to insult Mr. Madley?"

Malcolm stared at the floor and mumbled in a weak whisper, "Yes sir."

Hermione went on and explained how Malcolm had not been able to breathe, a condition cured by the creative Potion-brewing skills of Harry Potter. Snape was clearly skeptical, but when asked, Malcolm and two Slytherins in the crowd confirmed Hermione's statement. Snape finally looked directly at Harry, who stared back.

"How did you know how to fix his throat?" Snape demanded, sounding accusing.

Harry answered truthfully. "Because I had read Professor Figg's research on using Potions to cure curses, and she said that even the simplest Potions can sometimes be cures."

Snape grabbed Malcolm's robes and hauled him to his feet. He examined Malcolm's face and inside his throat, muttering to himself. "No permanent damage. No scars, once this Bubotubor pus is wiped away. But I still don't understand." He released Malcolm and looked at Harry. "You never seemed to listen during Potions classes."

"I did," said Harry. "And I studied Potions during the summer."

"You weren't allowed," said Snape faintly.

"I was staying with Professor Figg," Harry said, adding for no reason at all, "my godmother."

Snape looked as if he'd been struck. "Professor Figg? Your godmother? Of course, she always liked Lily." He seemed to have forgotten who Harry was and where they were, because when he spoke his voice was reflective. "She taught me too, years ago."

"I know," said Harry. "She said you were her best student."

Harry thought that Snape came perilously close to smiling. Then suddenly Snape seemed to come back to himself. He looked round at the students gathered there in the middle of the hall. "What are you all doing, standing here?" he barked, making them all jump. "Get out of here!" The students scattered. Snape seized Quentin Madley and Malcolm Baddock as they tried to run. "Not you. You two and I are going to have a little discussion with Professor Sprout." He turned to Harry. "Potter."

"Yes Professor?" Harry said, and felt Hermione tense up behind him, both thinking that a rebuke for messing up his Potions equipment was imminent.

But Snape just stared at him, frowning, not in anger, but as if puzzled. "One hundred points to Gryffindor," he said unexpectedly. Harry's mouth dropped open. Snape gave him one last searching look, then whirled and strode away, dragging the two boys behind him.