AN: I had a great time with this story, and I hope you have as much fun reading it as I did writing it. A big thank you to the mods of the Interhouse Fest for all the hard work, and thank you to my beta Raistlin for all the support. Any remaining mistakes are my own.
Charlie conquered the steps two at a time, ignoring the taunts of Sir Cadogan, who had been following him for the past half a dozen portraits demanding a joust, a duel, a trial by combat. Charlie had had the nerve, the temerity to accidentally bump into his portrait and nothing but bloodshed could satisfy the demands of honour.
Turning a corner, Charlie spotted Percy and immediately turned back, choosing to take the long way around instead. After McGonagall's lecture and Snape's detailed enumeration of his many shortcomings as a prefect, a Quidditch Captain and a student at that school, the last thing Charlie needed was to be scolded by his humourless little brother.
Sir Cadogan abandoned his quarry on the fourth floor and went off in search of more accommodating foes, and Charlie proceeded undisturbed until the seventh floor.
Tonks did not look up when he walked into the otherwise deserted room. The witch turned another page of her magazine, oblivious to his arrival. Even at a distance, Charlie could hear the loud music blaring from the Muggle contraption covering her ears. How she got it to work at Hogwarts he'd never know, but she'd been carrying it around since their first year. ("It's a Walkman." "I don't know what that means." "It's like Muggle magic. Listen.")
Charlie fell down on the mountain of pillows next to her. Without looking away from her magazine, Tonks pulled down the thingymajigs covering her ears.
"'Sup?"
Music kept on playing, loud enough for him to hear, but too low for him to make out the words.
"I've got detention from now till the end of term."
That got her attention. "Why?"
"Greengrass tried to hex me."
"Why did he try to hex you?"
"'Cause I'm sleeping with you."
"So is he."
"I believe that was his point precisely."
Tonks rolled her eyes and put down the magazine. "If he tried to hex you, how come you were the one who got detention?"
"'Cause I have better aim than he does."
"'Atta boy. A teacher saw it?"
Charlie nodded with a sigh, twisting the corner of a pillow between his fingers. "Snape."
He needed to say no more. It was common knowledge that Snape, who always turned a blind eye to Slytherin transgressions, took a perverse pleasure in punishing Gryffindor ones. Hannah Bell was still polishing trophies and suits of armour seven months after having accidentally pushed Eustace Avery into the Black Lake. ("But I didn't see him, Professor. Honest.")
"That's what you get for going straight," Tonks said, philosophically. "Karmic retribution."
"I didn't go straight."
"Oh really, Mr-we-can't-replace-the-school's-entire-quill-supply-with-profanity-quills-because-that'd-be-wrong?"
"I'm a prefect!"
"And a dull one at that."
"Where would we even get those many profanity quills?"
"We'd have managed if you hadn't chickened out."
"You're just bitter because Sprout picked Grace Macmillan for prefect instead of you."
"That's the sort of piss-poor attitude that landed you in detention, Weasley."
"No, a Bat-Bogey Hex landed me in detention, Nymphadora."
Tonks burst out laughing, despite herself. "You went with Bat-Bogey? Sweet."
Charlie grinned back, rather smugly. The horrified look on Greengrass's face had almost made detention worth it. Almost.
"I'm coming out of retirement, Tonks."
"Are you indeed?"
"One last mission."
"But you're a prefect now."
"Something for the history books."
"And a Quidditch Captain. Responsible-like. Respectable."
"A Gryffindor-Slytherin showdown."
"You're practically Percy."
"They'll never see it coming."
"You're rusty and out of practice."
"You'll help me."
"But I've replaced you with two new, shinier models."
"Fred and George are rookies. I have experience on my side."
"Yes, but they're naturals."
"I'm a natural too."
"Naturally prone to follow rules and respect your elders."
"You're a cruel, heartless woman."
"My mother was a Slytherin. It's in my blood."
Charlie wrapped an arm around her waist, pulling her to his lap.
"I'll have you know I have many, many advantages over my eleven-year-old brothers."
Tonks giggled when he kissed her, her hair turning a deep shade of pink. His hands followed the shape of her legs up her thighs and he felt the witch smile against his lips.
"Charles Septimus Weasley," she said, pulling away, "are you trying to bribe me with sex?"
"Yes. Is it working?"
Tonks laughed, kissing him again. "Too early to tell. Insufficient data."
"Good thing we have time, then."
"It lacks imagination," George said.
"It lacks ambition," Fred added.
"It does lack a certain…" Tonks paused, searching for the word. "Panache."
Charlie could feel a headache coming on.
"It's grounds for expulsion ten times over," he said. "It lacks nothing but common sense."
"Nonsense." Tonks flipped through the pages of the leather-bound book. "They wouldn't expel us for this. That's how you know it's a lacklustre idea."
Charlie sighed, frustrated. There had to be a good idea out there. Something that wouldn't get them expelled or killed. Or at least unlikely to get them expelled or killed. After three hours of endless debates, he was willing to compromise.
"Wait," he said, grabbing the book from Tonks.
"What?"
He turned back the pages to the image that had caught his attention and pushed the book to the middle of the table, so they could all look at it.
The twins frowned, but Tonks smiled the big, wicked smile of someone who could see nothing but possibilities.
"The common room?" she asked.
"And the dormitories."
"Charles, my darling, there may be hope for you yet."
"But how do we get in?" Fred asked.
"And what about the Slytherins?" George added. "There's always people there. Even during class."
Charlie and Tonks grinned at each other and Tonks morphed her face into the sharp, sour-looking features of Professor Snape.
"Messrs Weasley," the false Snape said in a slow, menacing tone, "when I give an order I expect it to be followed to the letter. It is not for little children to question the motives of their betters."
Fred and George stared open-mouthed at the witch, before exchanging an amazed look.
"Wicked."
Olivia Bletchley's day was not going well. It had started off poorly when Violet Crawley had decided that shrieking like a banshee at the crack of dawn was an acceptable way to start the day
"But there was a rat, Liv! I swear."
"Oh do be quiet, Violet. It was probably a house-elf."
"The size of a rat?" Josephine Davis smirked, catching Olivia's eye in the mirror.
"A very small house-elf."
"Or a very big rat."
Trying and failing to remind her hair that gravity existed had done nothing to improve her day, nor had the sudden realisation that she had forgotten to write her Transfiguration essay. No one could ever accuse Minerva McGonagall of playing favourites with the school Houses, but Olivia was certain that she could detect a gleeful glint in the old woman's eye whenever she got the chance to dock Slytherin points.
So instead of enjoying her free period out on the grounds with everyone else, the witch had camped out in the Slytherin common room, writing furiously in a race against the clock. A very contrary, very unhelpful clock.
As if being stuck indoors with all the losers who didn't have the good sense to go out and enjoy that glorious spring day wasn't bad enough, her work had been rudely interrupted by none other than her Head of House.
"But Professor, you don't understand." Everyone else had scurried away the minute Snape ordered them to, but Olivia wasn't as easily intimidated. Her father was an important man, and she had an essay to finish.
"I understand perfectly well, Miss…" He frowned, as if his failure to remember her name was somehow her fault.
"Bletchley, sir."
"Miss Bletchley. But the fact remains you have to find somewhere else to finish whatever it is you're doing."
"But why—"
"Are you questioning my orders?"
"No, sir, but—"
"Ten points from Slytherin."
"You can't—"
"Twenty points from Slytherin."
Olivia banged her book shut and got up in a huff, gathering her things. Difficult, horrid man. Her father would hear about this. Hurrying to the library, the witch pondered the many ways in which half-bloods were very clearly deficient in the most basic forms of courtesy and good breeding.
Had Olivia stayed behind, she would have been most surprised at seeing Severus Snape usher Charlie Weasley into the Slytherin common room. She would have been even more surprised to notice the two identical eleven-year-olds that followed him in.
Olivia saw nothing at all, however, nothing but rolls of parchment and stacks of books. It was not until much later in the day, when she was done with classes and her assignment had been safely handed in, that she noticed that something was amiss.
The crowd gathered at the entrance of the Slytherin dungeons parted to let by a very harried-looking Mr Filch, closing again behind him. Olivia pushed past the horde of Slytherins, Ravenclaws, Hufflepuffs and Gryffindors, muttering something about ill-bred peasants under her breath. Her self-righteous indignation at having to elbow her way to her own common room was short-lived. The witch stopped dead in her tracks the moment she made it through the door.
Filch was conferring with the Heads of Houses in a corner, gesturing wildly at the room around him, but Olivia paid them no mind. She could only stare at the Slytherin common room, which was entirely upside down. Sofas, armchairs, tables, even bookcases and footstools, they were all hanging from the ceiling, as neatly positioned as if someone had decided to tidy up and simply forgot which way was up and which way was down.
And to add insult to injury, the somber Slytherin green and silver tones had given way to garish reds and golds.
"Masterfully done," Tonks said, surveying the crowd from a distance.
"We've outdone ourselves," Charlie said proudly.
"Stories will be told of this day."
"Students years from now will sing our praise."
"I still say we should've flooded at least one of the dormitories." Fred waved his hands emphatically at the entrance of the dungeons. "The lake is right there!"
Charlie mussed his little brother's hair. "Ah, the eagerness of youth."
Just then the crowd parted to let the four Heads of House pass. McGonagall was the first one to spot them across the hall, but it didn't take more than a second for Pomona Sprout to look their way.
"They've got nothing on us," Charlie said, nervously.
"Not a thing," Tonks agreed in an uncertain voice. "Perfect plan. Flawless."
"Nymphadora," Professor Sprout called. "A word in my office."
"You too, Mr Weasley," McGonagall added. "Let's go."
The two of them exchanged a defeated look and made after the four teachers, who had not waited to see if they would follow. Fred and George, knowing when to make themselves scarce, had disappeared.
The crowd around the entrance to the Slytherin common room had not dispersed, and was now eyeing them curiously as they walked by. A Gryffindor third-year was the first one to start clapping, and the sound was quickly drowned by the thunderous applause and cheers of all the other Gryffindors, Hufflepuffs, Ravenclaws and even some Slytherins.
Tonks started giggling, and soon both her and Charlie were trying very hard not to laugh as they followed the somber teachers away from the still-cheering crowd.
"Totally worth it," Charlie whispered.
"Not a doubt in my mind."