Black Sheep

To the Dark Lord,

I know I will be dead long before you read this
but I want you to know that it was I who discovered your secret.
I have stolen the real horcrux and intend to destroy it as soon as I can.
I face death in the hope that when you meet your match,
you will be mortal once more.

R.A.B.

Sirius left when he was sixteen years old, and nothing was quite the same after that. In a way, Regulus began to understand just what had made his older brother, always so strong and resilient, crack. It had been easier being the younger son, the one who had no obligations. If he had shunned the family's beliefs as Sirius had, maybe he would have gotten off lightly. Because he was the son they did not need to have, the child that could have done whatever he liked and gotten away with it. And hadn't he done just that? How often had Sirius paid for his mistakes? How often had Regulus let him?

He was swimming in regret now, at the end of his life. Because Sirius had been right when he tore those clippings from his wall and called him an idiot. He had followed blindly his entire life, and the one step he took for himself had led him here, to a dark cave and a foul potion with his last words locked tightly inside a cheap fake locket.

In the cacophonous darkness that had poisoned his mind he saw Sirius leave, saw him from behind the eyes of a Death Eater's mask. He felt the brand on his arm burn with a newfound shame, like his very soul had been marred by his stupidity. He saw through his own eyes the many times his parents had treated his brother with varying levels of cruelty and he had just stood by and pretended it wasn't happening, that he had somehow done something to deserve it.

And he watched as he sent Kreacher off to what had almost been his death, and he felt the Dark Lord's cruelty in a way he never had before.

This final act, this painful severance, was a middle finger to his old Master of the magnitude that Sirius would have been proud.

But he'd never know. No-one would. It was the way it must be. He was a Slytherin, not a Gryffindor. He was never meant to go out in a blaze of glory, but rather wither away silently with his own legacy.

The potion had taken every last drop of moisture from his body, or at least it felt as though it had. He was thirsty in a way that felt inhumane, and he clawed his way across the damp rock to the water's edge, reached forward.

And the water reached up towards him.

Spindly fingers closed around his wrists, around his arms. They tugged at his robes and he fell into the water, screaming, fearing for the life he had willingly laid down. The water was cold as it rushed in around him, and the hands that tugged at him were colder still, blind eyes blinking at him, rotting teeth gnashing at nothing.

There was a light up above, and he closed his eyes to welcome it, to welcome his oblivion. Maybe now he'd finally be at peace. Maybe now they'd be safe, they'd all be safe.

Maybe with him, the bright edge of the Dark Lord's hope would begin die.

Only he didn't. The water rushed away as quickly as it had claimed him, a stronger, firmer hand gripping his ankle. And he hit carpeted floor with an almightly thud, a resounding crack filling the air.

The light had gone, the darkness spread in a less ominous way now. He did not recognise his surroundings; some old deserted building. There were no sounds, not even the distant rumble of Muggle traffic or passing footfall.

He did not know where he was, but he know one thing, clearly, distinctly; he was alive.

'Master Regulus,' croaked Kreacher's voice. 'Master-'

'I gave...you...an order...' Regulus gasped. Every inch of him hurt, and a new part began to ache at the lingering memories drenched up by the potion.

'And Kreacher has the locket,' Kreacher said. He held up one hand and the old locket swung from its chain. 'Kreacher switched them, like Master said.'

'You were supposed to leave me there,' said Regulus. 'I was supposed to...'

But Kreacher shook his head so fast his ears swung with the motion.

'No, no,' he said. 'Master said to switch the lockets and return home without him. But we are not home.'

Limbs shaking, Regulus propped himself up on his elbows and looked at the House Elf. There was a glint of something in Kreacher's eye, and he knew that he had deliberately misinterpreted his orders. Sometimes, Regulus forgot how crafty the old elf could be, and how specific one needed to be when telling him what to do.

'Kreacher, you were to leave me there!' he hissed, careful not to alert anyone who may have been nearby. 'Do you even understand...'

Images of possibility ran through his mind, of Kreacher being dragged to the depths with him, of the locket falling too...of his attempt to destroy the horcrux only serving to conceal it further.

'Kreacher is sorry, Master. But Master is alive. Kreacher will go home now. And he will have a cup of tea ready for Master when he joins him.'

Today was meant to be the day that he died, the day that he secured his family's safety. He was supposed to be known as the coward who fled the Dark Lord's service and died for his efforts. His plans were shattered, his image of the future warped.

What was he to do now?

AN - Been toying with posting this idea for a while. It started out as musings and I never intended it to turn into a full-blown story but it has! Basically it's an AU based on the idea of Regulus surviving the cave and being able to pass on knowledge of the Horcruxes to the Order of the Phoenix, thereby changing history.
Future chapters will be longer. Please let me know what you think, and if I should continue. Feedback is always appreciated and makes for a better story :).