This takes place after the war; Voldemort is gone, and Harry is alive, but not unscathed. He face was burnt, and now he's lost it. Snape died while working on a potion to cure Neville's parents.
'I laughed when you died, you know. I thought, 'serves him right, that git.' You were a git. You liked to make us suffer, you sardonic bas --- Well, you were wrong about me. Wrong, wrong, wrong, WRONG. I'm not like my dad at all. I don't even look like him anymore. Got my bloody face blasted off, didn't I?
'You're laughing from your grave, aren't you? Admit it. You know you are. You're laughing at me like you used to when I made 'soups for potions'. You think I deserve this. Sitting nice and cozy in your little grave, your ugly hooked nose leering up at me. Finally time I got retribution for being such an arrogant little prat. How dare I look like my dad. How dare I try and save someone else's life, right? It's not me that's lying six feet under in a stupid coffin, is it? It's not me that ended up running into a centaur --- after everything you've done. Couldn't fight off a stupid horse, could you?
'But, you've still got your face. Not like me. You think you've won now. You've got the last laugh, and here's me, sitting by your blasted grave to bring you those flowers you wanted. Neville's parents are still drooling over candy wrappers in a hospital ward somewhere and it's all YOUR fault. Couldn't even get your own blooming flowers without getting yourself done in, could you?
'You know, I don't think I'll ever understand you. One minute you hate me, the next you're making salves for my face and telling me it's not my fault. I wish it was your fault. I wish I still had a reason to hate you. You took everything, but I can't hate you. I can't hate you, you git. Yeah, you heard me. I called a dead bloke a git. What are you going to do? Give me detention? Take some house points? Go ahead. I don't think the counters work for DEAD men anyway. You're welcome to try . . . . I . . . I'll come tomorrow, bring those roses you needed.'
The place was empty once more. The boy who came every day, crying sometimes, laughing and shouting on others --- he would be back again tomorrow, bringing the promised roses. He would sit by the stone and shout abuse and sob and wish for a way to go back and change everything. He never would find a way to change it, but he would come back every morning at dawn, flowers in hand.
He would read the inscription on the stone and bawl like a small child. He would trace the carved letters with his fingers, the words he knew so well.
Great sun above, Good sod below,
Protect these bones, watch fast this soul.
For, here lies one of noble head.
'Tis a pity none knew until he was dead.
Nor brave man, nor bold may ever compete
With a Potions Master toiling over boiling heat
Here lies Severus Snape, a man of much power.
He went too far in his search for flowers.
'I brought those roses, professor.'