The Dark Mark burns and I apparate to the Dark Lord's side. What will he ask of me this time? A potion made, a Muggle killed, a half-blood tortured? How will I lose the next piece of my tattered soul?

But such questions are foolish, and I curtly remove them from my mind, bringing forward the old memories from when I was eager to do my Lord's bidding, when I was excited to be ordered into his presence, before I understood what he truly stood for. They sit at the forefront of my mind, and when I appear before my Lord there is nothing for him to read in me but zeal. I have no time for anything else, for it would mean my death. There is too much left to do for me to die yet.

"Severus," he greets me, as one might a favoured pet. I bend and kiss his robes, the perfect Death Eater. When I stand and step back from the dais, Lucius scowls at me from behind his mask. "I have a surprise for you, Severus," my Lord tells me. "Lucius has brought me a gift."

Two Death Eaters step forward and I turn to face them: between them they hold a thin, battered body dressed in oversized Muggle clothes. I see blood-soaked black hair and feel a jolt of disbelieving realisation. It can't be him! My Lord watches me carefully, and so I turn disbelief into anticipation. The head lifts and green eyes bore into me. His mother's eyes.

How in Merlin's name did they get past Albus's protections?

"I am astounded, my Lord," I bow to him. "May I ask how you managed to evade the Muggle-loving fool's defences?" My whole bearing is subservient awe, while somewhere in the back of my mind, so deeply buried that even I am barely aware of it, impossible plans whirl in frantic panic.

The Dark Lord waves to Lucius, who steps forward proudly. "I located the house he spends the summer in, and spoke with his relatives. They were quite willing to hand him over, even before I offered them gold." His voice is full of smirk. "We retrieved him yesterday; we haven't even touched him yet, his injuries were a farewell gift from his ‘loving’ relatives."

His relatives? Those clothes, that thinness, those injuries - his relatives? Did Albus know? Did anyone know?

Potter stares at me, with that same fire I called foolish pride, that same defiance I dismissed as cheek. That drive I loathed as brattishness that may be the only thing keeping him from collapsing into the arms of his captors. His eyes are bloodshot, making them a bizarre combination of Gryffindor red and Slytherin green.

"I had assumed - Dumbledore knows nothing of this." My surprise is genuine.

"Of course he knows nothing," the Dark Lord says, pleased with my reactions. "The old fool thinks he knows everything, but he is easy to hide from." He smiles half-maliciously at Potter. "Isn't he, Potter? He never suspects, does he? And when you try to explain, he doesn't believe you, does he, Potter? So you stop trying. And then when he finally asks, you deny it. Isn't that right? You're not the first he has failed." He steps down from the dais, coming to my side. "We are very much alike, Potter."

"You've told me that before, Tom," Potter says quietly.

"Ah, yes, my younger self. He liked you, Potter. He thought you had... potential. But you killed him."

"You can't kill a memory, Tom."

They are so calm, speaking together as if they weren't bitter enemies. Had anyone else dared to call the Dark Lord 'Tom' they would be guaranteed hours of torture followed by a slow death. And where is Potter's defiance, why is he not shouting and abusing the men who have him captured and the man who killed his parents? Where is that angry Gryffindor righteousness?

"My offer still stands, Potter. Despite what you've done against me."

"I thought you wanted to kill me. Wouldn't that prove your strength to everyone? Wouldn't that kill their hope?" This is the boy I called a spoilt brat, talking calmly to the Dark Lord about his own death?

"Ah, but how much sweeter to bring you over to my side. How much better to show them their hero has become heir to a Dark Lord. For you would be my heir, Potter, that is what I am offering you. Ultimate power."

"I thought you wanted to live forever, Tom. An heir would be nothing more than a rival for power."

"Not you. You... you are loyal, Potter. If I could bring you to my side then you would stay there."

"But first you would have to bring me to your side, Tom. I am loyal. And my loyalties are already decided."

I expect my Lord to be furious with this refusal, but he only laughs, with something akin to true amusement. "Tell me, Potter, did the Sorting Hat have difficulty with you? Bravery of a Gryffindor, mind of a Ravenclaw, loyalty of a Hufflepuff, cunning of a Slytherin. And a power all your own."

"It did offer me Slytherin," Potter acknowledges, and I gape. My Lord looks at me with that amusement.

"You didn't suspect, Severus? He could have been in your house. Would you still have hated him so fiercely if he had been?"

"I - I don't know, my Lord."

"The houses are meaningless anyway," Potter says.

The Dark Lord looks at him with interest. "Why do you say that?"

"People don't fit into boxes like that. And there are plenty of people who don't really fit any of the houses. It's very narrow-minded."

"Are you insulting my ancestor?" The Dark Lord sounds curious rather than angry.

"Actually, the Hat was Gryffindor's idea. And that would be our ancestor, Tom."

Should I just leave my mouth hanging open for the rest of the evening?

My Lord looks at me again, still amused. "Is this informative for you, Severus? Since he arrived yesterday, Mr Potter has told me many interesting things. But for you, I am sure this is all even more surprising. You must agree that Lucius has brought me an appropriate gift." He turns swiftly and returns to his chair. "But I invited you here for a different reason, Severus. I thought of how much you loathe Potter, possibly even as much as I did myself, and I though that you might like to help me enjoy the gift Lucius has been kind enough to bring me."

My mouth goes dry. "I live to serve you, my Lord."

"Of course you do, Severus. Potter, do you know who it is that stands before you?"

"I'm not an idiot, Tom. It's Professor Snape."

"Excellent. Remove your mask, Severus." I do so, and Potter's eyes flick over my face. "Then, Potter, you will know who it is who is torturing you. And if by some chance you escape me, which I will admit you seem to have a knack of doing, then you will know which of your teachers works for me, and you will hate him even more than you already do. But if you go to Dumbledore, he won't believe you, because that is not what he does. You will tell him it was Severus who tortured you, Severus who is a Death Eater, and he will tell you that ‘Professor Snape proved himself during the last war’. He trusts Professor Snape.”

"He also trusted my aunt and uncle." There is a surprising lack of bitterness in his voice. Had I been sold out by my family to a Dark Lord who had been trying to kill me since I was a baby...

"So we all know just how useful Dumbledore's trust is. Are you sure you won't join me, Harry?"

"If I agreed then you would know I was lying."

"True. Very well, Severus, try to make him scream. I think he'll be a challenge, won't you, Potter?" He leans forward, and Potter stares back at him calmly. "Release him." The goons stand back. "Make him scream, Severus."

The boy doesn't flinch as I raise my wand, and I am surprised by it. If this is Potter, then who have I been haranguing all these years? I hesitate, and he frowns at me; I take a breath and he relaxes. "Crucio." He wobbles, but somehow stays on his feet. He doesn't scream. I try again, putting more force behind the curse. He goes down on one knee, but his mouth stays shut. He stares at me, as if daring me to do worse.

I try other curses, ignoring the small voice howling inside me, trying to break him, trying to make him scream, knowing that I cannot stop until I do so and hoping he will just give in instead of trying to beat me. Why is he doing this to me? Why is he not breaking, why is he making me hurt him and hurt him and hurt him? The Dark Lord watches with pleasure as I become more and more inventive in desperation. And still the wretched boy just writhes on the ground, refusing to scream.

And then finally, finally, he shrieks, a horrible, otherworldly sound of pure pain that makes Lucius and the other Death Eaters take a step back.

"Well done, Severus," the Dark Lord says. "It is a pleasure to watch you work."

Not a pleasure. Not at all. "Thank you, my Lord."

"You may return him to his cell. Crabbe, show him the way."

I stoop and pick the boy up roughly, causing him to whimper. My Lord smiles in approval. I feel his eyes on my back as I follow Crabbe out of the room. Once we have left the others behind, the boy leans his head into my shoulder. "Thank you," he says, so quietly I can barely hear him. "Don't blow cover."

And I wonder again who this boy is.