Winter came, and with it came the dark.

It crept closer every day, dark that came too early in the evening and left too late in the morning, a hungry dark that always wanted more hours than it was allowed. One day, Moody knew, it would creep too far, and then the whole day would be consumed – all the light that struggled even now to keep the dark away, and there would be nothing left.

There were those who said he was obsessed with the dark, peering into shadows, seeing it everywhere he looked with a sharp bright eye and with magic piercing every cloak of invisible night.

They knew so little about him, even now. When he peered into shadow he wasn't looking for the dark, but for the light. That was in truth his one obsession though many looked and saw only paranoia and absence of moderation in his thoughts and actions. He knew that and did not care. There were always more important things to worry about than thoughts.

Other people complained that the holidays came too early, but he found himself rejoicing in it. Not because of the gifts that Christmas brought, because he never received any, nor because of the family who tended to cluster on such occasions, for he had had none of those left for a long time now, but with holidays came the lights. First there was Halloween with its jack o'lanterns – tiny candles burning valiantly in hollowed out pumpkins, their light flickering as the dark tried to snuff them out. Then there was Guy Fawkes, and he watched as people let off their fireworks, rockets screaming their defiance at the blackened sky. They exploded, gold and silver sparks showering, still glowing crimson phoenix like as they fell towards the earth, burning the last of their energy to keep the dark back. Bonfires burnt brightly all over the country, and people drew closer to the circle of light they created, clustering together as though for safety.

It was a war, he liked to imagine sometimes, a war that humans fought with light and with noise, roaring at the sky in one glorious night of battle. We shall hold you back! the fireworks shouted at the sky. Advance as you will, come as close as you dare, even swallow the day whole if you can, but still we will fight you. We carry the light, and we are not afraid.

It never lasted though. Brief and beautiful as a shooting star trailing fire over the horizon, the effort would fade leaving nothing but glowing afterimages in the memory. Even the most enthusiastic adults grew tired, the most excitable children were sent to bed, and the most annoying of teenagers eventually ran out of fireworks. Somewhere around three in the morning, the fire-engine sirens hat were so often an essential part of any good Guy Fawkes Night died down, and the bangs and flashes stopped. They left behind them only the stillness of the night, and the dark. After everything else had left, there was always the dark.

When everyone else had gone to bed, he stayed up still, stepped out into the cold night of night, and lit up a packet of sparklers one by one outside his back door. They would crackle like stars and he would write lost names in magnesium light watching them fade one by one into the darkness. As acts of defiance went, it was a fairly small sad one, but sometimes that's the only type you have left. Not until the last sparkler had sizzled out did he turn to go to bed.

Deliberately, he left every light in the house on as he passed on his way to the bedroom. He could have used magic to achieve the same thing of course, but he was working among Muggles for now, guarding them from that other darkness, the one they would not recognise even if they were to see it. There was a difference between being that strange man who never turned the lights off in winter, and the man who everyone had seen perform magic to keep the lights on. The electric bill would be huge, and perhaps that woman down the road would come and lecture him about the environment again, but it was worth it. The darkness could press just as thickly as it liked against the windows, but it would come no further. Not if he could help it.

After Guy Fawkes came Christmas, and people said that started earlier every year. He was glad of it, needed it, felt a little safer every time he saw one more house draped in the delicate little fairy lights that came with the season.

Some people felt the need to go further than that. The further into December they moved, the more of those houses that sprang up – houses that festooned themselves with light; huge inflatable glowing snowmen and reindeer, brightly lit Nativity scenes, flashing coloured lights that were spread over garages and roofs.

Everyone's opinion on those scenes seemed to be different. Some people looked at them and saw a garish waste of money and energy, others loved them and thought they contributed to the spirit of the season. Moody looked at them and saw something else entirely – people like him, fighting to keep the dark just a few more steps away from their homes, building a glowing halo of light to shield themselves. Perhaps they didn't know it, perhaps they didn't understand the ancient instinct kindled the first time a caveman set a spark to wood, but each one fought back in its own small way, shouting their message back into the darkness. We who love the light are not afraid. We can keep you back. We willnot let you in.

Amazing what instinct alone could bring about in Muggles who had no idea what it was that they were fighting, only that they needed to win. For those brief moments he wasn't alone in his efforts and sometimes he felt like he was the only one even trying so they were rare and precious things. Islands of light were reaching to each other forming a web that would contain the winterdark.

New Year began with one last battle. Again, fireworks tore through the sky, their bright flare scattering light everywhere they fell. Moody stood outside with them, listening to the gasps of wonder as each one launched, and turned his face up to the sky. Rockets, firecrackers, fountains, Catherine wheels – at times the multicoloured flashes seemed to almost drive the dark out entirely, and he smiled at the cheers of the people around him, even if they didn't understand what it was that they were cheering.

Strange that only days after such triumph the same Muggles seemed to vanish light from their world entirely. Christmas lights came down, put away in cupboards for another year, and the dark days truly begun.

It was enough to make him shiver, enough to make him want to shake them, and ask them how it was they could fail to understand that this was the very last time they should stop. They had reached the new year safely yes, they had survived that far, and yes the end to the dark days was close. Soon summer would be here, light would triumph again and days would turn from hurried periods pressed into the darkness into long lazy things with evenings that seemed to stretch forever. But they were not here yet, they had not beaten the darkness back yet, and it was not wise to stop fighting before a fight was won. That was the way to snatch defeat from the jaws of victory, if ever there was one. Constant vigilance, that was the key. People never understood – the vigilance was for the growing of the light as much as the presence of the dark.

It pressed closer now, as though knowing that this was its last chance before the clocks changed again, before its hours were cut back and it was controlled and defeated for another year. Dusk was the worst time, for looking into that unnerving half-dark, shapes could be made out, drifting shadows that could spell danger or could be nothing at all. Sometimes Moody saw things in the shadows that he had seen before, the last time the darkness had almost won, and never wanted to see again. Sometimes he saw painful illusions, the almost-shapes of friends lost and gone and a love that uncurled a brief glorious blossom in the cold of winter. His Christmas Rose, stolen by the dark of the killing New year frost. Darkness could be so cruel with its tricks, swirling a Pensieve of silvery half-thoughts from the winter mists..

Some people, he knew, thought that he was paranoid – perhaps even a little mad. He wasn't going to argue over something other could not grasp. Even wizards did not always understand the need to fight, the need to hold against the darkness. They had not fought as he had, they had not lost so many friends, they had not known how close it had come to swallowing the world and never releasing it.

He might have envied them, those people who were not afraid of the dark because they did not understand it, if only he hadn't wanted to shock them into understanding the danger. Ignorance was an easy road, and knowledge the hard painful track. But in the end the hard way was never as hard as the easy way. One day the darkness would return, and they would not be ready.

It was years before Moody had learned to control the dark, years before he managed to teach himself that light wasn't always something you needed to carry around in the form of a lit sparkler or a glowing wand. Light was something you could carry around inside you, even in the darkest of places.

Conversely, darkness could spring from anywhere, even the shadow at your back as you stood in bright sunshine.

He took that lesson with him, and tried to pass it on. Decades passed safely, and he never forgot the darkness. When Voldemort returned, into a summer that had lasted years without his disturbance, Moody remembered and was ready. He knew the oldest of magics and superstitions. Light was bought by blood in winter, blood in the snow and frost. When he fell, fighting against darkness that reached for him, darkness that laughed its triumph at finally succeeding, he carried the light with him and was not afraid.

With or without him, summer would come again.