Set during Snape's last year of Hogwarts.
Snape liked to wander the castles many twisting corridors at night. He liked watching the moonlight shine through the high windows, making his shadow ripple as he walked. He liked getting lost in the magical labyrinth that was, truly, his home. He liked to shuffle by with his hands in his pockets, letting his own confused thoughts swim around in his mind. It was the only way he could get peace these days. Snape's life had took such a turn lately that he often doubted he'd ever have truly a quiet moment to himself again. He knew it was his fault, he knew he was mixing with all of the wrong people. But Snape was finding that as the days wore on, the less he gave a damn about anything anymore.
The sound of laughter suddenly curled itself around the corner, and Snape stopped in his tracks. They were contrasting sounds, and as Snape listended closely to the peals of giggles clashing with the deep chuckles he realised that it was a boy and a girl. Walking slower still now, he turned around the corner and followed the laughter. It lead him to an empty classroom, where the desks were pushed against the far wall and broken pieces of chalk littered the dusty floor.
He could see now that the girl was sat on one of the desks, her legs swinging in rhythm to her laughter. The boy was stood in front of her, leaning in closely, his palms gripping the edge of the desk. Neither of them had noticed Snape appear in the doorway.
"Oh James, you do make me laugh," The girl whispered.
Snape froze. He'd know that voice anywhere, and as realisation hit him he wondered how he had managed to not recognise the laughter before. It was Lily. Snape crept closer and the scene before him slid in to a clearer view. He could now clearly see Lily's red hair glinting softly in the light of the moon and her eyes sparkling like emeralds in a treasure chest.
James Potter stopped laughing and launched forwards, planting his lips against Lily's. It was more than Snape could bear to watch. He had heard rumours that Lily and James were fooling around together, but until know he had preferred to pretend they weren't true. Snape felt his heart clench as something icy slid down in to his stomach.
Scowling, he stormed from the room, his cloak whipping at his ankles.
What Snape had just witnessed in that room was the perfect example of why he no longer gave a shit.