Regulus is ten years old and he is sad and disappointed. He had so hoped to go meet his aunt and uncle and cousins, to celebrate Christmas with the extended Black family, and now - thanks to his older brother, of course - it does not look like they will be going anywhere.
"I don't want to go, and I'm not going!" Sirius is shouting, stomping his feet, and spilling Floo Powder all over the living room floor. "This is stupid!"
"You are going, and you will behave yourself in front of your aunt and uncle, you disgrace to the name of wizard!" Their mother is shouting back.
Even his father is getting involved: "If you start behaving yourself right now, we might not punish you further than making you clean up!"
Sirius grabs a handful of Floo Powder, runs into the fireplace, and shouts "Diago-", and then their mother grabs him and pulls him out and gets dirt all over herself.
"Why can't you be more like your brother?! Look at him - he's been ready for half an hour!"
Sirius is looking at Regulus, and he is angry. "Because Regulus is a stupid and ugly little git," he says, while looking directly at Regulus, "and an idiot who has to do whatever I tell him because I'm the oldest!" He keeps talking, and he gets louder and louder. "He's probably a Squib too!"
Sirius has already gotten his letter and he has been showing off at every chance. "I'm not a Squib!" Regulus is about to cry. "So you admit that you're stupid and ugly and an idiot?" Sirius retorts in triumph.
"I'm not! I'm not!" Hot tears are running down Regulus's face now - he's humiliated. At least Sirius will be out of here next year, he's thinking.
"Yes you are, yes you are, yes you are!" Sirius is shouting, and he is advancing on his little brother, and their mother is screaming again, and her whole face is contorted: "The House of Black has never produced a Squib!"
"Yes it did! Regulus is a Squib!" Sirius yells with increasing satisfaction. Regulus knew they were not going to go over to his aunt and uncle's. He is climbing up the stairs and nobody is noticing him. The best place to go when they're fighting is in dad's study - the books muffle the screaming.
Regulus pulls out a book from the top shelf with his mind. I'm not a Squib , he thinks to himself. He reads about a wizard whose name was Harpo the Foul, who had encased his soul in an object so that he could not be killed. There is a passage there that Regulus doesn't understand. His parents are shouting even harder, and despite not following the book, Regulus is concentrating very hard, so as to not hear them. "The Horcrux cannot be physically destroyed, and ordinary magic cannot affect it. It must be destroyed beyond physical or magical repair, or else its maker cannot die. Only the most powerful Dark Magic can destroy a Horcrux." What does that mean? Regulus asks himself. He doesn't know what it means, but keeps reading anyway. Then, Kreacher pops into the room.
"This is not a proper book for young Regulus," the elf says. "Regulus is only a child - he should not be reading this."
"I don't care," the child says, and his eyes and nose are still red. He hates being the youngest, he hates having Sirius for a brother.
"Regulus is not a Squib, he will be a very strong wizard, he is a good boy, he will make Mistress Black proud, Kreacher can tell!" Regulus brightens a little, and he puts the book away and never gives it another thought. Only when he will be too sleepy to control his thoughts, will he remember that he has ever read such a thing, about a wizard who put part of his soul in an object that could not be destroyed.
When the fight ends, mum and dad go look for Regulus, and they don't even mind that he snuck up to the study, and they praise him for being a good son, the pride of the family, and they make sure to say within Sirius's earshot that Regulus is nothing like him, that he understands what it means to be a Black, like they always do. Regulus only smiles and he doesn't know what he did, besides not causing trouble. He wishes his parents would tell him that, even if Sirius ever behaved himself. The more Sirius misbehaves, the more they lavish Regulus with presents and praise, and this infuriates Sirius, who takes it out on Regulus, and worse - on Kreacher, and it keeps getting worse and worse. He cannot wait for his brother to go to Hogwarts already.
The locket had not responded to anything they had tried to do to it, not even when all three of them cast their most powerful Reducto curse at the same time. It was indestructible, and yet it had to be placed in the middle of a lake, in a cave that was only reachable by magic, and was protected by an army of inferi and a whole bottle of the Drink of Despair? It could be only one thing.
"I know what this is," Regulus said, suddenly.
Severus and Lily stared at him. "It's a Horcrux," he said.
"A what?" Lily asked, and even Severus was confused.
"A Horcrux, I read about them, um, once. They contain a fragment of a soul, so the maker cannot be killed. That's his most bitter enemy - it's death!"
"That's impossible," Lily said, although she had gone a little pale. "Everyone must die."
"Not him," Regulus said, darkly. He had read about Horcruxes, but his child mind never realized they were real, that it was in the realm of magical possibility, that anyone could be so terrible as to protect themselves against death by committing murder - destroying their own soul, to become immortal.
"You make them by committing murder," Regulus added. "I wonder who has had to die for this."
"Well, he's killed so many people by now, it could be anyone -" Lily said.
"It has to be murder without motive - it has to be for pleasure, or it won't split the soul. Some innocent had to die for this, and give their life - for the Dark Lord to be immortal." Regulus hadn't realized he had memorized the words he had read all this time ago. I must have really wanted to get away from the fighting, he told himself. Only now did he understand what he had read - how terrible it was, what Kreacher had meant.
He didn't make us take a vow because he cannot be killed, Severus realized. He can afford to play games and hunt traitors down. If Regulus was right - and Severus believed he was - whom had they knelt before, whom had they now resolved to fight? Could it even be done?
"We have to take this to Dumbledore," Lily announced. "People in the Order are fighting against him and now you're telling me that he can't die -"
"I'm not taking anything to anyone," Severus protested. "And neither is Regulus, and neither are you. We'll be killed instantly, if we're lucky. And Dumbledore will want to know where you got this from."
"Sev, I'm going. He's going to start wondering about James at some point, what am I meant to tell him? He knows he didn't actually send him on any mission, and Sirius will start sniffing -"
"And I'll bet his sense of smell is much better than it was," Severus interrupted, remembering that Sirius was, after all, part canine now. "Fine. You go. But you can't mention us."
Lily was not sure how she would avoid it, but she promised she would. This is for the best. Dumbledore has to know, she told herself.
Lily decided that she wouldn't tell Albus what she thought she was bringing him. He might have another theory, she thought. Something not quite so hopeless.
The closer she got to Albus's office, the more the locket seemed to struggle - absurdly, Lily felt like it was scared. It did not want to meet Albus, it shook and resisted as though something was trapped in there, and was helplessly being dragged along to its doom.
"Lily!" Albus exclaimed. "I hope everything is well! How is James doing? Well on his way to a full recovery, I hope?"
Immediately, Lily started crying. Finally, she was alone with someone who didn't despise James and who didn't try to kill Severus - someone who could recognize that she had lost something, and that it hurt, even if she wasn't sure she wanted it any more. But she had to keep her promise and not tell Albus how James ended up poisoning himself to death.
"James died - I can't tell you how it all happened but it's the truth - he died to get this." She struggled to put the locket on the table between her and Albus. "You-Know-Who was guarding this very heavily and James died to retrieve it."
The locket seemed to want to get away from Albus, who could not touch it, but he recognized it. He had seen it before on his former student, Tom Riddle. This was indeed Lord Voldemort's - Lily had somehow made a difference in the losing war.
Very few people knew that Tom Riddle and Lord Voldemort were one and the same. Lord Voldemort himself had obscured his, and Albus had long decided to play along, since Tom Riddle was remembered much too fondly, as the student who had found the monster who slaughtered Myrtle Warren and saved the school. Only Albus knew the truth, and he could never prove it.