The moment Snape uttered the word, Slughorn's jovial expression froze solid.
He stared at the boy in disbelief, his pudgy fingers tightening involuntarily around the stem of his goblet. Slowly, with a dry tongue, he licked his lips and croaked, "What did you say?"
"I asked if you knew about Horcruxes, sir." Snape's tone remained calm, conversational, as if discussing the weather. With a flick of his wand toward the door, he cast a Muffliato charm, then tucked the wand back into his robe.
"What do you need your wand for?" Slughorn's voice shifted, losing all warmth. What had been genial now brimmed with wariness and defensiveness.
"Muffliato, sir. Prevents eavesdropping. A distinguished Auror once told me: 'Constant vigilance.'"
"Oh, fine, fine," Slughorn huffed, waving a hand impatiently. "But this isn't a matter for you, my boy."
He paused, and when he spoke again, his tone was sharper. "I know nothing about Horcruxes. And even if I did, I wouldn't tell you! Out—out! I don't want to hear another word of it!"
"Nothing at all, sir?" Snape ignored the order and took a step closer. "I simply thought… if there was one professor in Hogwarts who might offer insight into such advanced magic, it would be you. That's all. I just wanted to ask."
"You thought wrong!" Slughorn snapped, his face twisting with disdain. "You made a mistake—a very big one!"
He reached out, as if to physically shove Snape from the room.
"Did I, sir?" Snape stood his ground, voice cool as stone. "That's a shame. I had hoped to ask what should be done if one were to find a Horcrux within the castle."
The colour drained from Slughorn's face, his expression crumbling into something pinched and haggard. His round features seemed to sag under some invisible weight.
"What… what did you say?"
"I found something in the castle," Snape repeated, enunciating each word with deliberate force. "Something that matches the description of a Horcrux I read in the Restricted Section."
"What book?" Slughorn fumbled in his breast pocket and drew out a handkerchief to dab at his sweating brow.
"Secrets of the Darkest Art, by Owle Bullock," Snape said flatly.
"Oh, Dumbledore…" Slughorn groaned aloud, unusually calling the headmaster by name. "That book shouldn't be there!"
"But it was there, sir. If I found it, others can too."
"Perhaps… yes… perhaps," Slughorn muttered, dabbing his forehead furiously. "Though I know nothing about Horcruxes, as I said. Still, as Head of House, I could at least look at this… thing you've found. Where is it?"
"If you know nothing—absolutely nothing—about Horcruxes," Snape said, locking eyes with him, "then there's really no need for you to get so worked up, is there, sir?
"In that case, I'll simply take it up with the headmaster directly."
"I'm not worked up!" Slughorn's reply came too fast, too loud, and his voice cracked mid-sentence. "Yes, yes, Albus—go to him if you must—but I can help too!"
"I would very much value your help, sir," Snape replied, softening slightly. "That's why I stayed tonight. But we have to be honest with one another, don't we?"
"You're far too clever for your own good, Severus." Slughorn muttered, stuffing the handkerchief back into his pocket. "That curiosity of yours—it'll land you in serious trouble someday.
"These things… they are vile. Unnatural. What exactly is it you want to know?"
What do you mean I shouldn't be clever? Snape thought bitterly. If you old men weren't so hopeless, I wouldn't need to shoulder this burden.
He could be watching Pandora brew potions, or sipping oak-matured mead at the Three Broomsticks. Anything was better than facing these wrinkled, evasive relics of a failing world.
The entire magical society of Britain was still sitting on its hands, hoping a baby would someday save them, cheering quietly in the shadows every time his parents dared to speak the Dark Lord's name aloud.
It was pathetic. Someone had to take action. If not me—then who?
How could progress happen with nothing but Flobberworms around him?
This was for the survival of more than just himself.
Snape refocused, staring into Slughorn's eyes. "Just out of curiosity, sir. I want to know if a soul can only be split once—or if dividing it more times would be more effective."
Slughorn's hand jolted violently, knocking his goblet to the floor. It shattered with a sharp crack.
"What did you say?!"
Sweat rolled freely down the professor's face now. One trembling hand dove into his pocket again, retrieving the handkerchief far more slowly this time.
"You—" Slughorn now looked genuinely frightened. His voice shook. "Why are you asking that kind of question—?"
"Also asking?" Snape latched onto the slip like a hawk. "So someone else asked you the same thing before, didn't they, sir?"
"No one!" Slughorn snapped, panic mounting. "No one asked me that! I don't know! I don't know anything!"
"But you haven't answered, sir," Snape pressed, his voice calm and clear. "Why would someone leave a Horcrux somewhere anyone might find it?
"Horcruxes are supposed to be incredibly rare, valuable. So… I wondered. Maybe the creator made more than one. What do you think, sir?"
Slughorn staggered back, bumping into a chest of drawers. Several bottles wobbled ominously atop it, rattling against one another.
"How many times can a soul be split, sir?" Snape continued mercilessly. "The person who asked you before—what did you tell him?
"According to Bridget Wenlock's theories in Arithmancy, seven is the most magically powerful number. So… seven pieces, perhaps?"