Even before she became apparent, he knew Lily was in his presence. He could feel her behind him, like a glowing orb of golden light which overwhelmed him and made him falter. She filled him with joy and warmth, easing the pain and overpowering his dark thoughts. She was his angel.
All his instincts were telling him to turn around and embrace her, but Severus knew better than to listen to them.
Severus had taught himself to control his emotions, circling them around his body, never letting them spark his features. He knew that letting his instincts rule over him would lure his emotions to the surface, and the aching hurt he locked away would break free of its hold. Sometimes he wondered if it was selfish of him to not let himself experience pain, when others hurt so easily.
There was one key to unlocking the mystery of Severus Snape, and that was a feisty red-head, Lily Evans.
Lily could read Severus, even when he couldn't himself. Severus thought little things went unnoticed by her, that her headstrong, passionate nature shrouded the tiny details. Severus was wrong. Lily noticed every little detail about him, every weakness.
She noticed the hunger in his eyes when he worked his potions, she saw the annoyance twitch through his temple when Potter would try and flirt with her, she distinguished the colour of his cheeks when his black met her green, and from time to time she would glimpse his wounds through the crinkles on his forehead. She acknowledged each and every one of these slips, fastening them to her memory, sometimes not knowing how to react, but perceiving them. What she didn't realise was that soon she would miss the shoot of pain crossing his face as she suppressed a laugh with his ridiculers.