The Mirror: Lily's Eyes

From death, she casts her spell...

He hadn't known it was in the castle.

The Mirror of Erised...It shows us nothing but the deepest, most desperate desires of our hearts.

He moved toward the mirror until he stood directly before it.

And there she was, her image so clear in the glass it was as though she stood before him. She just looked at him for a moment. Then she smiled, green eyes sparkling. She looked so...alive that he almost thought if he smashed the glass that she would step out as though nothing had happened. But another thought stopped him:

Lily Evans has been dead for ten years.

She placed her palm on her side of the glass. He reached out, but tore himself away and hurried out of the room. He couldn't stop himself from looking back at the door.

Lily had vanished.

...

"I have spied for you and lied for you, put myself in mortal danger for you. Everything was supposed to be to keep Lily Potter's son safe. Now you tell me you have been raising him like a pig for slaughter -"

"But this is touching, Severus," said Dumbledore seriously. "Have you grown to care for the boy, after all?"

"For him?" shouted Snape. "Expecto Patronum!"

From the tip of his wand burst the silver doe: She landed on the office floor, bounded once across the office, and soared out of the window. Dumbledore watched her fly away, and as her silvery glow faded he turned back to Snape, and his eyes were full of tears.

"After all this time?"

"Always," said Snape.

- from Harry Potter and the Deathly Hallows, chapter thirty-three "The Prince's Tale"