Disclaimer: Her Highness Rowling owns it all
Why wasn't the potion purple? It was supposed to be purple. Hermione's was purple, Neville could see over her shoulder. His potion was, well, the color of vomit, and frankly his stomach felt like he could add a little more to the cauldron at any moment. Snape was making his way down the row of students toward him, and as the sneering face got closer Neville's vision started to cloud. Snape paused longer than usual at Hermione's cauldron, trying desperately to find something wrong with it. This turned out to be Neville's saving grace, for just as Snape was finishing with Hermione, the bell rang. Neville threw his potion ingredients into his bag and booked it. Only halfway across the great hall toward the marble staircase did he remember that he had left his cauldron full of potion in the classroom.
//Snape's not going to be happy about that one. Detention, you think?//
//I don't care. At this point, I'll be doing detentions for him halfway into the summer.//
//But, I don't think they can make you stay in the summer.//
//Believe me, if Snape could find a way, he would. And Gran might not argue with him, either. I can hear her, "If the professor thinks it would be beneficial to your education, Neville Longbottom, you will stay at that school as long as he says. You should thank him for this opportunity for your improvement." Wouldn't that be awful?//
//You know she means well.//
At this point, Neville realized he hadn't been paying any attention whatsoever to where he was going, and was now in a completely unfamiliar corridor. H sank down with his back to the wall.
//I can't even find my way around this place, and I've been walking this same route after Potions for five years!//
//Well, Snape was particularly rough on you today.//
//It's not just being scared by Snape, I did the same thing last week after Charms, and if I've ever been scared by Professor Flitwick I'll transfigure myself into a mandrake right now.//
//Well, it's no use just sitting here. You might as well get up and try to find your way back. You don't want Filch finding you, I'm sure he'll have some reason you're not supposed to be here.//
Neville got up, heaved his bag over his shoulder, and started walking.
//No, no, I'm pretty sure it's the other way.//
//Fine. I'll just follow you, since I know nothing. Neville, Neville, he knows nothing, for his head is full of stuffing. I heard a Slytherin second year reciting that to one of her friends. Would you like to hear the rest?//
//Oh, give it up. You can't possibly take a Slytherin second year seriously?//
//But everyone knows it, even if they don't say it.//
//Neville Longbottom, you stop that this intant!//
//Oh God, you sound like Gran.//
//Shut up! You are not worthless, or stupid, or friendless. You are very good at Herbology, and a good and loyal friend. Hell, how many other people can truly say that they're friends with Harry Potter? Not bloody many! So stop moping for yourself.//
Neville had reached the portrait hole, and stared at it blankly for a moment.
//Right, the password! Ummm… Boomer-something, no… Burnt beets, no… I can't remember.//
//Oh, come on. You can't even… //
//Bouncing balls, no that's not it either. Damn!//
"Butterbeer," said a voice, and the portrait swung open. Ron turned his head as he started to climb through and noticed Neville standing there, mouth slightly agape. "What are you doing out here?"