This is a prequel to JK's books written before DH, the answer to the question beginning with 'Why the hell …' is different in my longer fic (which I will post if I ever get round to proofread it and if I find a title. A title would be nice.). I have, however, adopted one character of that: a house-elf with very unusual manners. There's a story to that in my book six, but not here. Deal with it.

Severus stared into space. This was definitely not what he had wanted. In fact, at the moment he had no idea what he wanted. He dropped into a chair and buried his face in his hands. 'Why are you so worried?' asked a high voice behind him, and Severus jumped.

'Get away from me. I've been telling you that for ages now.'

'Make me.' Severus raised his wand and turned.

'Fine, should I?' Before him stood a small being with bulging lamplike eyes and huge ears. 'Go home, Sneek.' The house-elf ignored the wand pointed at her and dropped into a chair. For any other of her kind this would have been more than indecent behaviour, but she would only have laughed if she had been told so.

'You know, I don't like that name, you could call me Constancy. That would be a good name for me.'

'Very good for a slave that took flight.'

'I didn't take flight, I found a hat.'

'It was a handkerchief. See, Sneek …'

'Oi, Severus, please!'

'Fine, Constancy, leave me alone! I have other things to do than to chat with a runaway house-elf.' He dropped back into his chair and ignored the disappointed look on her face.

'I really want to help.' He huffed.

'Good. Undo my mistake.' Constancy frowned. Not that he could see her, but he knew anyway.

'What have you done?' A sense of deep satisfaction filled him when he realised this would finally get her off his back. When he spoke, his voice was deep and quiet and filled with a very clear threat.

'Hah, now I'll get rid of you. I sold James and Lily Potter to the Dark Lord.' Constancy smiled mildly.

'Why don't you want to tell me the truth?' He gave her a fierce look.

'This is the truth. Look here!' He pulled up his left sleeve and forced Constancy to stare at the Dark Mark burning on his forearm. She backed away from him, looking frightened.

'I never knew.' Severus pointed his wand at her again.

'I'll not have you sell me to the Ministry. You're done talking.' Constancy screamed and crouched on the floor, covering her face with her hands. For a moment he had planned to actually do it. Kill ber, blast her to smithereens … Only, he couldn't. Why the hell that was he had no idea, but he couldn't destroy the stupid little thing. Severus lowered his wand. 'Stand up. That position doesn't suit you, it's confusing to see you being subservient. Stay if you like. Leave if you can't stand my presence any longer. I don't mind.' Constancy rose slowly.

'You need more help than I can give you.' Her voice was shaking slightly. 'But there is someone. Go to Albus Dumbledore.' Severus laughed mirthlessly.

'Sure, he of all people will help me.

'What do you want? You did not want them to die, did you?' Severus shook his head. 'Good. If there is anyone who would give a traitor like you a second chance, it is Dumbledore.' Slowly, Severus nodded.

'You are right. I'll go there. If I don't come back …'

'I will go looking for you and plead for your life if I must. Go now that you are determined to, now, before you lose your nerve.' Severus nodded again and left at a run. He needed to get to Hogwarts as fast as he could.

ϡ

'Albus, tell me now before I get angry.' Alastor's voice was even more gravelly than usual. 'Someone must be responsible, and I know you well enough to tell that you know who they are.'

'Why are you so sure that someone of my acquaintances has done this?'

'Because you look like that.'

'Are you never wrong? I didn't say I knew who it was.'

'All right, then I will assume it was you. I have to arrest you for betraying Lily and James Potter's current whereabouts to Voldemort.'

'You know I could not have told him that if I had wanted to.' Dumbledore's voice was gentle and understanding. It was maddening, really.

'All right. But who betrayed them to him then? The location he knew from Black. But you clearly hinted that someone must have told him to seek them in the first place.' Dumbledore shook his head.

'I just didn't want to believe it,' said he softly, when the door flew open. Alastor had his wand in his hand instantly, pointing it at Severus Snape, who had just stormed in. The young man backed away when he saw the Auror glaring at him.

'What is he doing here?' he asked.

'What brings you of all people here? That's the question that comes to my mind,' Dumbledore asked unusually coldly. Alastor looked from one to the other.

'It's him! Don't say it's not, Albus, I am an Auror.' He approached Snape, pointing his wand at the younger man's heart. 'One movement.' Snape froze. 'Was it him?' Dumbledore nodded. 'Good. I hereby arrest you in the name of the Ministry of Magic for betraying the Potter family to Voldemort and for being a Death Eater.'

'No, please!' said Snape. 'Professor Dumbledore, listen to me! Only a minute, please!' Alastor made a wild gesture with his wand that shut Snape up.

'You'll have time enough to ponder your defence in a cell in Azkaban before your trial.'

'Sit down, Severus,' said Dumbledore. Alastor frowned at him. 'You too, my friend. We will hear him out.' Alastor's eyes narrowed.

'Have you lost it? He is a Death Eater or he would barely have told Voldemort anything. He is responsible for this … Albus!' Dumbledore nodded slowly.

'I know. Please sit down, both of you.' They obeyed, and Dumbledore dropped into a chair opposite to them and interlocked his fingers. 'What did you mean to tell me, Severus? Alastor is my guest today and I will certainly not send him away.' Snape glanced at the Auror, who looked positively like a hyena smelling prey. 'I take it you are a Death Eater?' Snape nodded.

'Yes, but I didn't want this to happen.'

'Why did you betray them, then?'

'I didn't betray them! I didn't even know they were there!'

'I know you couldn't tell him that. But you told him about my conversation with Sybill. The one you overheard.' Snape nodded slowly.

'Naturally,' said he, and Alastor snorted. 'But I never knew it was about the Potters.' Dumbledore silenced Alastor with a gesture.

'I happen to know that you were enemies.'

'Yes, but I didn't want them dead!' shouted Snape. 'I don't like that Auror either, and I don't kill him.' Alastor gave a humourless laugh.

'I'd like to see you try.'

'If I had known it was about them I wouldn't have …' Snape's voice failed him for a moment. 'I knew them! Professor Dumbledore, I would have told him anything about people who were complete strangers to me, I admit that, but never about someone I had known for so many years.' Snape hurried around the desk and dropped onto his knees before Dumbledore. 'You must believe me, I didn't want them dead. If I could undo this, I would, at once. I would tear that Mark out of my flesh, I'd never join him if I had the choice now.' Snape closed his eyes, and for a long time Dumbledore merely looked at him.

'I believe you, Severus,' he said then. Snape's eyes flickered open, but before he could say anything, Alastor was on his feet.

'How naïve are you? That man is spinning you a tale, don't you realise that? He knows that you'd give him to the Ministry, so he comes and tells you he regrets what he did, and tomorrow he'll go to Voldemort and tell him to kill you!'

'Alastor stop shouting at me,' Dumbledore said perfectly calmly. 'You've been loud enough for the next three years. I do believe Severus.' He looked at the young man who was still on his knees. 'Stand up, I do not want people on their knees before anyone, certainly not me.' Snape rose and looked at Dumbledore. His features showed that he didn't really believe what was happening. 'You will teach here. This will keep the Ministry from asking questions. Alastor, give it a rest. And you will do whatever I tell you.' Snape nodded eagerly, and suddenly Alastor had an idea.

'I know a way you can be sure he does. I wouldn't entrust a class full of people to him right now, but there is a way.'

'I will most certainly accept any constructive suggestion from you,' Dumbledore said, and Alastor approached him.

'Let him make the Unbreakable Vow to you. It is the only way to be entirely sure that he doesn't turn his back on us.' Dumbledore slowly shook his head.

'Alastor, this is not the way I want people to be faithful.'

'I know, but this is the first time a Death Eater comes and claims he didn't mean to do what he did. If he refuses, you can assume he did no more than act just now. And if you don't ask him to, but appoint him, I will never have a peaceful night ever again.' Dumbledore smiled.

'I do not wish to be responsible for that. Severus, I must ask you to make the Unbreakable Vow to me.' Snape gasped. He had not expected that.

'I should … what?' Alastor growled.

'See?' Snape stared at both of them. Incredibly slowly he went to his knees again and looked at the floor. 'One moment,' said Alastor. He took a piece of parchment and scribbled a number of sentences onto it. He gave it to Dumbledore. 'That's supposed to be worded well enough.' Dumbledore read through the parchment before he knelt opposite to Snape. Their hands entwined, and Alastor stepped between them, placing his wand on their hands.

'Will you, Severus, instruct and encourage your students not to give in to the power offered by the Dark Arts, both in- and outside classes?' Dumbledore asked, reciting from Alastor's scribble. Snape's answer was slightly unsteady but clear.

'I will.' A bright fiery tongue emerged from Alastor's wand and wrapped around their hands.

'Will you do everything within your powers to protect the school, its students and the staff both from the threat of Lord Voldemort and the Dark forces in general and from the allurement to side with him or any other Dark wizards?'

'I will,' said Snape, firmly this time, and a second tongue joined the first.

'And will you do whatever I tell you and do your best to fulfil the tasks I set to you, not only but especially in order to serve the forces that stand up against Lord Voldemort and the Dark forces in general?'

'I will,' said Snape, looking Dumbledore directly into his eyes, when a third tongue came out of Alastor's wand. As he stepped back, the three fiery strings melted into Dumbledore and Snape's hands, leaving no visible sign but the knowledge that there was no way Snape could ever truly return to Lord Voldemort.

'The first thing I ask of you is not an order,' said Dumbledore when they were standing again. 'You need not follow it if you feel incapable. I want you to return to Lord Voldemort as a spy. I know this means a great danger to you, but I guarantee you that I will do my best to protect you, and should you ever think Voldemort suspects something, you return straight to me and I will take care that he doesn't get you.'

'I'll do it,' said Snape bravely. Dumbledore smiled and sat down behind his desk.

'We don't have a Potions master at the moment, I would like you to take that post.' For a moment Snape hesitated then he nodded.

'Of course, sir.'