There were hours in between the drawn curtains and morning breath that belonged only to us. First in a four poster bed, yours or mine, and no one knew we were magnets. Winter's night fell soft and light like a too-thin blanket. You found your way into my bed and I couldn't tell you how or why, just that it was warm and right and that the sweat dampened the hair at the nape of your neck so that by the morning you no longer smelled of soap, but of boy, of Sirius, and it was my favourite smell and no one knew.

Later, we took the night for ourselves. Both hands clasped around its throat, or each other's, and everything was red and thumped with an urgency that didn't belong to us. We didn't belong to us. We belonged to secrecy and to war and to grief and to power and to hope and to loss and only sometimes to each other. You said, things like "You're gorgeous," or, "Fuck me," or, "When we're old men, we'll have a cottage by a lake, a small one," softly to the space just below my ear and still no one knew.

War tightened like a noose. We hadn't yet discovered who slipped it round our necks and we four each scrabbled for purchase on cold stone. I thought often of that high tower, those four poster beds, and how I'd never felt safer anywhere. How your duvet swaddled me like a mother and that was enough then. How you crept from the bottom of the bed, slowly, laughing when I winced at every creak of the bedframe and shushed you. How the sounds of not just your breathing, but the snuffling symphonic snoring of my favourite people in the world, all under one rain-battered roof, washed me to sleep in their unending waves. So, years later, when war tightened like a noose, I lay alone and in the quiet and barely ever slept. And I thought of you, and how no one knew, sometimes not even me.

In the belly of the battle there is a new kind of hunger. It is one I could never look directly at, lest the wolf see and think himself welcome in me. But you – oh, you loved her. A hunger so primal, a need so sharp she felt like a knife to the gut. The hunger for victory, for glory. For the kill. I saw it in you and I pretended I didn't and this, we kept to ourselves, too. So many things we never said out loud, or at all, and that sounds like the same thing but it is not. So many secrets I pressed into the knuckles of your spine or burrowed into the warmth of the backs of your knees in the winter and so many questions we asked only by rough hands on soft skin. So many apologies we only gave with kisses, with cheek brushes, with our foreheads pressed together until your breath became mine became ours and nothing belonged to us again. We belonged to nothing again. All this, Sirius, and no one knew.

So when the night came that I, too, had been no one – when I, too, hadn't known – do you think I should have been surprised? That there was a secret only yours and I hadn't gleaned it from the pads of your fingers, or the jut of your hipbone. That you had said a careful nothing in between all of the nothing that you'd never said but meant. The hunger that came for us when we became cardboard soldiers and how I'd refused to meet her gaze – should I be surprised now that she had seduced you? When I had seen how you thrived in all this blood and all this red? When I had said nothing. When I had seen you stare with that dangerous glint, eyes blazing and wand drawn, and looked away. Left you to your intimacy.

And even after, I think, even when I'd feared the darkness that had the potential to overgrow like a weed inside you, even then, I held you. Or I washed your socks. Or handed you bowls of hot soup. Or said, "Be careful," or, "Come home safe," or, "I couldn't do this without you." All the little things we did or said that meant love without ever admitting it. The ways I asked you not to leave me.

You know, I said, "Goodnight," and slept and I dreamt of us every night. I dreamt of a life post-war, and the things we would do with the neverending scroll of free time. I saw you with a child aged Harry, rolling in the grass, other children running around behind you. I wondered if some of them were ours. I wrote sentimental poetry and it was all bad and all about you, and you made me tea and we wrapped blankets around our shoulders and sat by our lake. Our breath fogged in the winter and we took cool dips in the summer and I watched your handsome face harden, roughen, your jaw a straight line and your smile never one, and then finally, I watched you soften with old age. When I woke, you were always there. Eyes closed and snoring ever so slightly. You looked so very young. I longed for the gift of your every day. For the privilege of watching you grow old and fat and cranky.

I think often of that high tower. How we'd filled it with laughter and whispers and made love and had our first sips of burning firewhiskey. How our best friends became our brothers and Hogwarts our home. How two of the joyous voices now resounding in my skull belong to dead men because you were you and no one knew. I think of that four poster bed, and how you slithered from the bottom and wrapped yourself around me like a python. How you hissed at the space just below my ear. I think of the noose and it becomes your hand around my throat. I think of the hunger I couldn't give in to and I want to consume you whole, tear you limb from limb.

Except I don't.

I want to go back. I want to be fifteen and kiss you quick in the library, giddy at the thought that no one saw and giddy at the idea that someone could have. I want you to say, "When we are old men and you're wrinkled and I'm greying," and make up stories and I don't want to wonder whether or not you believe them to be anything more than fantasy. I want to believe you. I want, more than anything, to go back and unlearn the hitch of your breath in my ear. I want to unknow you without words. I want to forget your name by heart. But I can't, and I don't, and I hate you only almost as much as I miss you.

It is a mild spring night. I am lying on the dust of someone's uncle's sitting room floor. There are four days til the next full moon. All of my friends are dead. It is too quiet. I cannot sleep, and I love you, and no one knows.