Reality snapped back into focus with the distinctive echo of dripping water and ancient stone.
Sirius stumbled, catching himself against a damp wall. "Bloody hell! You can Apparate inside Hogwarts?"
"I'm special that way." Arthur's smile carried insufferable smugness. "Even the famous Black wards bend for me when I ask nicely."
"That's imposs—" Sirius's protest died as he took in their surroundings. "Where the devil are we?"
Carved serpents coiled along wet stone walls, their scales gleaming in the eerie green torchlight. Shadows writhed across the corridor like living things, and the ceiling vanished into darkness above, giving the impression of standing at the bottom of an enormous well.
"The Chamber of Secrets." Arthur's voice echoed strangely in the vast space. "Thought I'd take you somewhere truly private for our conversation."
"The Chamber of..." Sirius's eyes went wide as saucers. Whatever important discussion he'd planned evaporated like morning mist.
He spun in a slow circle, drinking in details like a man dying of thirst. His fingers traced ancient carvings with reverent wonder, following the sinuous curves of thousand-year-old serpents.
"Sweet Merlin." His voice held childlike awe. "James would have killed to see this. We searched for it, you know. Every secret passage, every hidden room. Never found it."
"Hard to find when you need Parseltongue to enter." Arthur gestured toward the main chamber. "Come on. The interesting bit's through here."
The main chamber opened before them like a cathedral dedicated to serpents. Monolithic pillars carved with coiling snakes rose into shadow, their eyes seeming to track the intruders' movement. At the far end, Slytherin's colossal face gazed down with stone eyes that held an unsettling intelligence.
"Merlin's beard." Sirius whispered. "Harry fought a basilisk in here? He was twelve!"
"Sixty-foot basilisk, to be precise." Arthur's tone was conversational, as if discussing the weather. "Should have seen the mess. Blood everywhere, venom eating through stone like acid, shed skin piled higher than a man..."
He gestured to the perfectly clean floor. "Took me ages to clean up."
Sirius's wonderment shifted to suspicion. "Clean up? You mean you harvested everything?" His voice rose with indignation. "That was Harry's kill! The spoils should have been his!"
"And let a magical beast rot down here? Please." Arthur shrugged. "It was either I harvested it or let time destroy it. Besides," he added with a smirk, "the profits funded a rather successful little venture of mine."
Sirius sighed, long and theatrical. "Fine. How much did you make?"
"That's between me and my vault."
"That's not an answer."
"It's the only one you're getting."
They stood in silence for a moment, Sirius clearly wrestling between curiosity and indignation. As always with a Marauder, curiosity won.
"Did you find anything else?" His eyes gleamed with renewed excitement. "Secret rooms? Slytherin's private study? His legendary library?"
"Searched every inch." Arthur shook his head. "Nothing. If it exists, it's hidden beyond my ability to find. Probably needs Parseltongue to access. You should have Harry come down and take a look. The knowledge within would be... invaluable."
Sirius nodded absently, still drinking in the chamber's dark majesty. Then his expression shifted, excitement draining away like water through sand.
"I almost forgot why we came here." He took a steadying breath and leaned against the ancient stone. "It's about Horcruxes."
The word seemed to leech warmth from the air itself.
"I've been investigating," Sirius began, his casual tone at odds with the gravity of the subject. "Dumbledore confirmed it before he died—Voldemort aimed for seven. Well, six Horcruxes plus his main soul."
He counted on his fingers like a morbid shopping list. "The diary Harry destroyed. The locket I handled. Whatever ring gave Dumbledore that cursed hand. That's three."
"Four," Arthur corrected mildly. "I destroyed Ravenclaw's diadem years ago. Found it in the Room of Requirement."
Sirius's jaw dropped. "You—when?"
"Years ago. Didn't seem worth mentioning at the time."
"Didn't seem worth mentioning?" Sirius's voice cracked. "Destroying a piece of the Dark Lord's soul didn't seem worth—" He visibly collected himself. "Right. Fine. Four down. I know Bellatrix has one. Tried to get it, but she caught on and my plan failed spectacularly."
Arthur was genuinely impressed. That Sirius had even discovered Bellatrix possessed a Horcrux showed remarkable investigative work. The man was far sharper than his reputation suggested.
"Does Voldemort know you're hunting his anchors?"
"Fortunately, no." Sirius grimaced. "For some reason, Bellatrix kept her mouth shut. Small mercies."
"Good for you. Otherwise you'd have the Dark Lord himself knocking on your door." Arthur's tone was light, but the warning was clear. "So. Four destroyed, one identified but secured. That leaves one mystery."
"Not a mystery." Sirius's certainty was absolute. "I have a theory."
Arthur tilted his head.
"Nagini." Sirius said. "That snake's too intelligent, too connected to him. All the clues point to it being a Horcrux."
"Impressive." Arthur allowed genuine praise to color his voice. "I didn't think you had this level of deductive reasoning in you, Black."
"Thanks for the vote of confidence," Sirius muttered.
Arthur smirked. "So. Did you call me here to brag, or are you asking for help with the last two?"
"Neither." Sirius's light tone vanished like a snuffed candle. "That's not why I asked you here. I'll handle those somehow."
The atmosphere shifted. Even the carved serpents seemed to lean in, stone eyes gleaming with anticipation.
"I think there's a seventh piece." The words fell like stones into still water. "An accidental one."
Arthur waited.
"Harry's connection to Voldemort goes beyond surviving the Killing Curse." Each word seemed physically painful. "The visions, the Parseltongue, the way he can see through Nagini's eyes... If Nagini's a Horcrux, and Harry shares that exact connection… then Harry is one too."
The silence that followed was absolute. Arthur slowly began to clap, the sound echoing off ancient stone like a death knell.
"Bravo, Lord Black." His voice was soft, almost gentle. "You've hit the nail precisely on the head."
Sirius staggered as if physically struck. His face went grey, aging a decade in seconds. "So it's true? My godson is... he's a Horcrux?"
"Not exactly." Arthur said. "I don't think it was a planned Horcrux. Just a fragment of Voldemort's soul that broke off that night and latched onto the nearest living thing. A soul leech, not a crafted vessel."
"Is that good news?" Sirius asked desperately. "Can it be removed? Without… without hurting him?"
"Yes," Arthur said simply. "I can do it."
Relief hit Sirius like a physical force. His knees buckled, and only the wall kept him upright. "Then do it. Please. I'll give you anything—my fortune, my properties, my life—"
"I could." Arthur raised one hand, stemming the flood of promises. "But before you start signing over ancestral estates, you and Harry need to decide if removal is truly your best path."
"What?" The word exploded from Sirius. "How could leaving a piece of Voldemort in my godson possibly be the right choice?"
"What if it functions as protection? An unwitting shield?" Arthur's calm was maddening. "I believe it was part of Dumbledore's plan."
"Dumbledore knew?" The temperature seemed to drop ten degrees.
"He knew. Of course he knew." Arthur's voice turned clinical. "But he had no way to remove it. So what's a chess master to do? Use it. Make it part of the grand design."
Understanding dawned horribly on Sirius's face.
"He raised Harry to be self-sacrificing." The words came strangled, torn from his throat. "Every trial, every test, every manipulated year—all to make Harry the kind of person who would walk willingly to his death."
"The initial plan, certainly. But something changed in Harry's fourth year." Arthur paused for effect. "In that graveyard, Voldemort used Harry's blood for his resurrection."
"So what? What difference does—"
"It created a unique magical paradox." Arthur's explanation took on a professorial air. "This is speculation based on magical theory and Dumbledore's actions, but I believe the blood connection created an unprecedented loophole. Now, if Voldemort attempts to kill Harry with the Killing Curse, the spell will target the foreign soul fragment first. It will destroy the parasite, not the host."
"You're talking about an extra life." Sirius's voice was hollow. "In the final confrontation."
"Precisely. A second chance when it matters most."
"How can you be sure?"
"I'm not," Arthur admitted. "But I am sure that this became Dumbledore's new plan. A terrible, high-stakes gamble, but a gamble nonetheless."
"I don't trust him," Sirius said, his voice raw. "I don't trust his plans or his gambles."
"Smart man." Arthur conjured two chairs with casual waves. "But now you have options. Dumbledore's portrait should activate within days. You could hear the full plan from the source. Then you and Harry can make an informed choice."
They sat in contemplative silence, surrounded by Slytherin's serpents and the weight of impossible decisions.
"You can definitely remove it?" Sirius finally asked. "Without Dumbledore's death-and-resurrection gambit?"
"Easily."
"What would you do?"
"Destroy it immediately." Arthur said without hesitation. "I would not tolerate another soul residing in my body, no matter the potential benefit. But then, I'm not Harry Potter."
"I agree," Sirius said, a new resolve hardening his eyes. "But you're right. It has to be Harry's choice, not mine."
"Then send Dobby with a message when you have decided," Arthur said. "I will come."
"You're doing this for us… how can we repay you?"
Arthur's lips curved into a rare, genuine smile. "Let Harry have a thorough look around this chamber with his Parseltongue. If Slytherin left any secrets behind, consider them my payment."
"Done," Sirius agreed instantly.
With a nod, Arthur grasped Sirius's arm, and the cavernous Chamber of Secrets dissolved around them once more.
They materialized on Hogwarts's grounds, afternoon sun shocking after the chamber's eternal twilight. As they walked toward the castle, Sirius made one last attempt.
"Any chance you'd consider returning to the wizarding world? Amelia would create a position for someone of your talents."
"Not interested." Arthur's rejection was absolute. "The wizarding world's too small for me. I prefer a bigger stage."
"Shame."
They parted at the courtyard—Sirius heading to find his godson, Arthur vanishing into the afternoon with another impossible Apparition.