He doesn't know I'm watching him; jet-black hair falling heavy into his eyes, face rapt in concentration, those thin, delicate fingers tracing their way across the page with the sound of spiders' footfalls. We've been in here for hours, now, and in that time the light has changed from burnished noon to amber sunset, falling in criss-cross patterns from the high windows, picking out the gold-leaved spines. He's researching something I can barely follow, my skills lying more in Charms than Potions - but still, he fascinates me. So I sit on the windowsill, pretending to research our History of Magic essay, watching every flicker of those glittering eyes.

The room is almost silent, the air expectant, as though waiting for someone to break the stillness. And what would it be broken with? Sev's voice, beautiful in its low silkiness, reading a passage aloud. His eyes amused. Or my own affected nonchalence, as I take of my glasses - an affectation, really - and ask if he wants me to suck him off? Oh, think of that - him pushed up against the Potions stack, thrusting desperately into my mouth, clawing for release.

On afternoons like this, we both need it.

He has a string of strawberry-red marks running up the side of his neck, normally hidden by the lavish sweep of hair. I know because they make me want to kiss him, to follow in Lucius's demanding footsteps, to show him that it doesn't have to be like this, it doesn't have to be about the pain. Like a trail of blood in the snow, they are; like that first winter we all went hunting at Lestrange's, and the quarry crawled for miles before we found it, quivering under a gorse bush.

He sidles into the library with his eyes all sleep-smudged, walking like he's still in a dream. And he runs his hand through my hair absently before he sits down, and I just want to shake him and cry: 'Severus, Sev, where are you?' Because he's fading around the edges after every night with Lucius. But still he comes to me when he's on the outs, when whatever Lucius can do to him just isn't enough. Spell-locked doors and silencing charms, and the sweet scent of Earl Grey lingering in the air, until the smell of tea always makes me think of him. And the way he always brushes the hair off his face afterwards with trembling hands, looks at the floor and whispers: 'I should go.' And no kisses, ever.

I wonder if he knows that Lucius kissed me. When we were both fourteen, before Lucius became the beautiful fucking golden boy, back when he was nothing more than a pretty pair of eyes and straggly blond hair. It was summer, and we were drunk on cherry brandy.

Then again, last summer. He was too lonely at home to sneer at my parents' nouveau riche tendencies, too damn needy to turn down an invite to a dinner party. And afterwards, behind the rose garden, the scent of rose petals in the breeze, Lucius Malfoy's hands in my hair. I remember how willingly he gave in, when pushed, and I wonder if Sev knows it too. How Lucius almost sobbed with pleasure as I fisted his cock with hands sticky from champagne, how he arched into my touch, how he begged.

Sev turns a page, and looks up. I smile, because for all that he's the serious academic he has ink on his lips, staining blue like a spreading bruise. One day I'll have him, too quickly to protest, my lips on his before he can cry out.

And the treacle light is catching brown flecks in his eyes, so cool and distant, and soon it will be time for dinner. He hardly eats. I'd love to cook for him, make him spend time with me over half a bottle of wine and a guttering candle. Italian, of course; pasta oglio e aglio, the subtle contrasts of rich, buttery olive oil and the sweet tang of garlic.

"What would you like me to do?" I whisper, the words hopeful in the dust and arcana of the library.

He turns a page, slowly, methodically, fingers skimming across the surface as if he could read knowledge printed deeper than paper. And my heart is hammering, though it shouldn't be. I want him so much that I can taste it, sweet scented tea and lingering traces of Lucius. I close my eyes, waiting for him to speak. To say how he will whore me, this time. How he wants me, illicit in the Potions classroom or hard and fast under the Quidditch stands. And this - this - makes me real.

I can hear the smile in his voice as he starts to reply.

"Rosier -"