He's running. The black cloak billowing out behind him, just missing his fingertips so that he can catch him. They've been at this game of cat and mouse for about six hours now; it's coming up to midnight. And Severus Snape is determined that this man will not live to see another day.
The cold beginnings of Winter are freezing at his chest, little clouds of air coming from his mouth, and his fingers stuck into a fist around his wand with the frost.
The man in front turns and shoots a spell over his shoulder. Snape swiftly ducks, the jet ruffling against his hair. His opponent curses himself, and tries again. Snape is more ready for it this time and manages to shoot one back. This too, misses. Now that the wands are being used again, the fight becomes more violent. A variety of colours, that muggles might mistake for fireworks, explode around the small and quiet neighbourhood. The man snarls at him, his yellow teeth shining in the light of the moon, before hurtling every spell that he knows at him. This time Snape has to resort to more muggle methods to avoid them, and rolls out of the way, before sending a flash of silver his way. The chains miss him, but the next blue spell shot doesn't, and he gasps, clutching onto his side in pain. Snape grins, taking the opportunity to wipe away the blood that is seeping down from the cut over his eye. He clearly spent too long at it though, because he feels a large punch in the stomach from a yellow spell that is, strangely enough, unknown to him.
The chase begins again, running faster than the muggles out enjoying their Christmas Shopping can see. They are invisible to those who do not wish to look. The man in front of him is a good runner, and a good duellist too, it has to be said. But he begins to lag behind a little, exhausted from six straight hours of running. He swirls his cloak around him and vanishes up into the night sky. Snape knows that trick and turns quickly, shooting the killing curse at the man who has reappeared so suddenly behind him, so as to spook him.
The man lies crumpled on the floor by Severus' feet, his eyes and mouth wide open in terror. More gently than he feels, Severus kneels and closes them, before standing again and throwing red sparks up into the sky to alert the Ministry to yet another murder.
He then walks away. He has no choice, no point in lying and pretending that he was only the discoverer of the body and nothing more. This is his job. For the Death Eaters, and for the Order of the Phoenix, he kills opponents. Which side does the man lying dead a few feet away belong to?
He doesn't even know anymore.