Disclaimer: nope, don't own this at all

AN: right, I generally feel almost guilty when I write Sirius with anyone but Remus - that's a bit weird really. Anywho, here's a little one-shot that's probably a bit OOC for Bellatrix but I tried to make her in character as much as possible. It's a bit AU too, as she's only two years older than Sirius and Narcissa is the eldest of the Black sisters -the story just worked a bit better that way. Please read and review :)

Sirius sat sprawled out on the green upholstered armchair, eyes closed, wishing fervently to be somewhere, anywhere else. The drawing room, usually the scene of most Black family gatherings, was empty for once - besides Sirius. The others were in the dining room for now, though they would most likely file into the drawing room later. Sirius sighed and shrugged off his robes, revealing Muggle jeans and t-shirt underneath. It was far too hot in this house to wear the dark robes his parents demanded.

'What are you doing in here?' a cold female voice demanded from above him.

Sirius cracked open one eye to see his cousin, Narcissa, regarding him icily. 'Nothing,' he said shortly.

'Insolent Gryffindor,' Narcissa said with disgust. Sirius shut his eyes again and showed his cousin his middle finger. A moment later, he heard her leave. Probably to see that prick, Malfoy, Sirius thought. The eldest of the Black sisters was engaged to the man, an idiot apparently, though Sirius didn't know him too well personally. Sirius tended to avoid any situations involving his cousins that he possibly could.

He grimaced, he knew that within the next few minutes he'd be booted into the dining room to make nice to people - Death Eaters and bigots - he barely knew because he was the Black heir and he 'better well do as he's bloody told or he'll regret it'. That was his mother talking of course. His father's words were much colder, measured, less frequent, more cutting. Sirius winced unconsciously at the thought of one of his father's admonishments.

'Cissy told me you'd be here,' a low, cool voice informed him.

Sirius's eyes sprang open, startled. Bellatrix. He forced his face into an expression of contempt that he didn't feel. He had to remind himself not to gawp at her perfect, velvet and lace clad body, her dark, slightly malicious kohl-rimmed eyes, her full lips wearing jet black lipstick. In her hand - with its red painted fingernails - she held a glass of dark red wine which she took a sip from now. Sirius blinked.

'What do you want?' he asked, still sprawled with a strange elegance upon the gilded armchair.

'I'm here to make you a proposition,' she replied, sitting opposite him on the sofa, legs crossed with the same Black grace that Sirius had in profusion. Sirius felt slightly uncomfortable in front of her, she was two years older than him and used that much to her advantage.

'Fair enough,' Sirius nodded, determining to look unimpressed. Bellatrix appraised him silently. Sirius shifted uncomfortably. 'What's your…proposal?' he asked finally, unable to take the silence.

'I've heard it from Regulus that you fancy me,' she said by way of an explanation, staring unabashed at the sixteen year old.

'Wh- what?' he spluttered.

'He heard you talking in your sleep apparently,' Bellatrix explained, smirking slightly.

'Little bastard,' Sirius muttered mutinously.

'No denial then?'

Sirius swore under his breath, but he shook his head. Bellatrix's smirk widened into a predatory grin.

But Sirius was confused. 'So? You said you had a proposition?'

'Patience,' she chided. 'I'm currently being courted by Rodolphus Lestrange-' Sirius nodded, he knew this of course '- and my parents are very happy about that, obviously, they helped to set me up with him. But they'd been happier if…'

Here she paused to take another drink from her crystal wine glass. Sirius gazed at her, hypnotised by her easy movements. 'Yes?' he prompted impatiently.

'If you were returned to the family-'

'I'm already in the fucking family,' Sirius said resentfully. But then his eyes widened as he realised what she meant. 'As in, by-…by marrying- oh fuck…'

'Yes, marrying me,' Bellatrix finished. Her expression changed from manipulative to bitter. 'My only use,' she said very quietly, too quietly for Sirius to hear.

'You want me to marry you?' Sirius checked.

'I want you to pledge your allegiance to the Dark Lord,' Bellatrix corrected.

'Yeah…shit…'

'Yes, I'll marry you if you join the Death Eaters and fight for their worthy cause, alongside me,' she added with a determined edge to her voice. She would become the only female Death Eater if she did so.

'But- but we're cousins,' Sirius protested weakly.

'We're purebloods Sirius, we're Blacks,' Bellatrix reminded him.

'I…really, I can't do that,' Sirius said, staring at her alabaster pale face in dread. He could just- he could marry her. He could wake up every day beside her and tell her how beautiful she was and make love to her and - but he couldn't. Not at that price.

Bellatrix met his gaze and held it for a moment before throwing her head back to drain her glass. She set it down on the small coffee table, and smiled, a cruel tint to it. She stood up and Sirius instantly mirrored her actions. Her head tilted to one side, she looked Sirius up and down as if deciding something.

'All you have to do,' she said, closing the distance between them with slow, deliberate steps,' is to join the Dark Lord.'

With that statement, she leant in and kissed her cousin full on the mouth, hard and insistent. Sirius took a moment to comprehend what was going on but once he did he kissed back eagerly, anxious to savour the only kiss he'd likely ever get from her. He wrapped his arm round her slender waist and tried to pull her closer but at that, she placed both her hands on his chest and pushed him away firmly.

'That's all you have to do,' she repeated quietly. Sirius watched her departing figure, wondering vaguely if it was actually possible to kick himself. He crossed over to stand in front of the mirror hanging over the impressive fireplace to see black lipstick smeared around his mouth.

Bellatrix sat on the fourth step of the back staircase, cursing herself. She had failed to seduce someone who already fancied her. Useless. She rolled back the sleeve of her black robes to reveal a sinister tattoo. She would not fail her master though. She would not be useless any longer.