Sirius let out that strange sound again, something between a laugh and a sob that belonged to neither category, and drove his fist into the side table hard enough to rattle everything on it. Then he was on his feet.
"Where are you going," Tom said.
"To bring Regulus home. I'm not leaving him in that cave." Sirius's eyes were red, and he turned toward Kreacher, who was still huddled on the floor. "You're taking me there. Right now."
Tom snapped his fingers.
Sirius locked mid-step and toppled back into his seat, Petrified. Kreacher found himself equally unable to move.
"I'm not underestimating you," Tom said, standing over Sirius and looking down at him with something that was almost patience. "But if Voldemort's trap was the kind of thing you could just walk through and come out the other side, he wouldn't be Voldemort. The Black family has already lost one person to that cave. You want to be the second?"
Sirius's eyes were the only part of him that could still move. They communicated very clearly that yes, if that was what it took, he was prepared to be exactly that.
Tom shook his head. "This is what I can't stand about you Gryffindors. Everything is a reason to throw your life at the problem. Can't anything get done without someone dying for it?"
He let a moment pass.
"Last time you made a clever decision in a crisis, you switched Secret Keepers. Do you remember how that ended? If you die today, Harry loses the last person he has left. Did that thought make it as far as your brain before you stood up?"
Another pause.
"I didn't say I wasn't going. I said sit down."
Tom had a gift for finding the exact point where a wound hadn't closed and pressing on it with precision. Sirius couldn't argue back, partly because his jaw was currently immobilised, and partly because there was nothing to argue with. Every word Tom had said described something that had already happened.
Tom crouched slightly to meet Sirius's eye level. "Are you calm? Because if you're calm, I'll go to Dumbledore. Anything connected to Voldemort, he'll help without needing to be asked twice."
Sirius blinked rapidly. Once, twice, three times.
Tom released the spell.
Sirius led him through the house to Phineas's portrait frame, which was currently empty. Tom called the name twice, then a third time.
Phineas appeared in the frame with the expression of a man who had been interrupted during something important. "Sirius, you absolute, you have the audacity to just" He stopped. "Riddle? What are you doing here?" His tone shifted completely. "You're the one who called for me?"
Sirius's mouth twitched. So when he called, he got lectured. When Tom called, it was warm curiosity. Perfectly reasonable. No notes.
"We've found a lead on one of Voldemort's Horcruxes," Tom said. "And information about your great-great-grandson Regulus. Don't ask me to explain everything now or I'll have to do it all again when Dumbledore arrives."
Phineas's expression went serious in an instant. He studied Tom for a long moment, then disappeared from the frame without another word.
The room settled into quiet. Sirius sat turning over the word Horcrux, trying to fit it against what he knew. That locket was a Horcrux?
Tom meanwhile had set the locket on the table and was examining it carefully, then called Ravenclaw into the space. A relic that old deserved a proper eye on it.
"Wait." Ravenclaw looked at it and frowned. "Isn't that Salazar's locket?"
She had recognised it immediately.
"How did it end up with you."
"I need to know something first," Tom said, not answering her. "Is this locket capable of anything beyond storage?"
Ravenclaw nodded slowly, thinking it through. "That piece has been in Slytherin's line since his ancestors. The symbolic weight always outweighed the practical function. He kept it on him, used it occasionally to store small personal items. Roughly equivalent to one of your carrying pouches."
"Someone has turned it into a Horcrux," Tom said, seeing no point in withholding it. "Voldemort's work. I was wondering whether the Horcrux enchantment might have overwritten the original function, or whether the locket simply never had any other function to begin with."
"A Horcrux."
Ravenclaw couldn't examine the physical object from inside the learning space, but the description alone was enough to shift her expression from curiosity to something sharper. Then, slowly, a look of grim amusement settled over her face.
"If Salazar ever finds out that his family's most significant heirloom was used as a vessel for a fragment of a Dark wizard's soul, he will personally ensure that soul spends a century roasting in hellfire."
Studying Dark magic was one thing. The Black family motto might as well have been ambition and blood, but Slytherin's was bloodline and glory. Having the family's defining object desecrated in that particular way was not a philosophical objection. It was a personal insult to the name itself.
The amusement faded.
Ravenclaw went quiet for two full seconds.
Then, carefully: "Tom. Tell me honestly. The Diadem. Has someone made that into a Horcrux as well."
Tom turned the locket over in his gloved hands. He did not answer directly.
"Rowena. You've said it yourself before. Sometimes being too clever isn't a gift."
"I see." She breathed in slowly. The smile that came after had nothing warm in it. "Voldemort. I have his name now."
Tom observed a private moment of silence on Voldemort's behalf. Being remembered with intent by a woman was one thing. Being remembered with intent by the single most brilliant woman in the history of the wizarding world was something considerably more consequential.
He almost felt sorry for him.
From the front of the house, the wind chime above the door rang out, clear and bright.
Dumbledore had arrived.