Disclaimer: If owned this, I wouldn't be on FF, I'd be filthy rich. I own nothing. Everything belongs to JKR.
Snape went immediately to the mirror room. "Damn cloak" he muttered speeding up his pace. The door was slightly cracked. He rushed forward, fully intending to throw the door wide open, when he heard something that made him stop dead.
"Mom?" Harry whispered as he looked at the mirror.
Severus froze. He felt like the world had just done a 360°. That was not what he expected to hear. "Lily." he breathed.
Harry jumped. The noise had startled him. Throwing the cloak on. He stood still for a minute. Clearly listening for any more noises.
Severus remained silent, cursing himself.
Hearing nothing, Harry exited the room, moving quickly. Snape drew back into the shadows.
Part of him wanted to go after Potter. The other half knew he couldn't. He let Harry go, just this once. Waiting until he was sure Harry was gone, he crept silently into the room.
There, the Mirror of Erised stood in all it's glory. He stood in front of it.
"Lily" he breathed, seeing her ghost. He sank to his knees.
"Lily."
