Disclaimer: I obliviously don't own Harry Potter or any of its characters.
AN: This is an idea that came to me last time I read Chamber of Secrets, specifically the flying car. I hope you enjoy, feel free to comment.
In a compartment on the Hogwarts Express, four fourth year wizards inspected the small collection on the table. There lay the pieces, that they had agreed to collect over the holidays, of the ultimate in wizarding pyrotechnics. James and Peter had each ordered a pair of fireworks from Dr. Filibuster, Sirius had created some mysterious wonderfully dangerous-looking explosive, and Remus- whose parents, it was decided, would be too concerned at their son purchasing explosives-had contributed a very complicated timing/ignition device.
"Sirius, what is this amazing thing?" James asked in awe holding up the homemade contraption.
"Cardboard tube, covered in layers of flashpaper, filled with color changing black powder and some powder I found in a box marked "dangerous", with a core of erumpet horn fluid."
There was a round of impressed whistles from the other three. "James, be very careful with that. That fluid is highly unstable and very explosive." Remus warned. "I'm surprised it hasn't gone off already."
"Don't worry, Moony. I've stabilized it, took some doing but a wrapping of dragon skin and a steady hand does the job." They all nodded approvingly at his genius.
"Mate, you're a genius!" James exclaimed, setting it back on the table. "That's our centerpiece!"
"So we strap the fireworks around it." Peter finished, pulling a reel of spello-tape out of his bag and adding it to the pile.
They spent most of the trip carefully attaching the four fireworks to Sirius' creation by their fuses then configure an ignition with the timer.
"Finished!" Sirius exclaimed, throwing up up his arms as Remus connected the final wire- completing the circuit between timer and battery ignition.
"This is going to be brilliant!" James added admiring the completed firework.
"When should we set it off? After exams?"
"No, Peter! Something this good can't wait that long to be used!" Sirius berated.
"I think it would make a nice ending to the start of term feast." Remus suggested.
"Perfect! I know we keep you around for a reason!" Sirius teased. "Always the best plans."
"And the best excuses." James added.
"Do you hear something?" Peter asked tentatively.
The rest paused to listen. A soft ticking came from their masterpiece. "Merlin's beard! The timer's started!"
"The circuit's complete, and someone started the timer." The four friends looked around at each other, any one of them could have hit the start button by accident, they had all had a hand in its attachment.
"We'll just break the circuit." Suggested Peter reaching to pull a wire loose.
"No!" Shouted Remus and Sirius simultaneously.
"Any fiddling now will set off the core!" Sirius further warned.
"Two seconds." James read out in warning. They all made to duck under their robes for protection.
As the train pulled into the Hogsmeade station, a magnificent explosion blasted in flashes of color and Catherine Wheels within the confines of the compartment.
Entering the castle the four walked side by sid, accepting the congratulations of people they passed. Sirius had come away entirely unscathed, Remus' hair was slightly singed in places, James' smoked faintly, and Peter had gotten the brunt of the explosion- face blackened and eyes full of shocked awe like Moses come down from Sinai-, but they all were grinning like idiots. They hadn't yet entered the Great Hall when their beaming swagger was brought to a flinching haltby a stern remonstrance from the corridor to the left.
"Potter, Black, Lupin, Pettigrew!" Professor McGonagall's voice carried sharply to their ears. The four turned down the corridor to face her, their oncoming doom.
"Hello, Professor." They greeted, trying to look as innocent as possible.
She took a shrewd look at them, her eyes wandering over their robes which showed obvious signs of burns. Opening the door of the nearest empty classroom she beckoned them in with a short jerk of her head. It was there her fury was unleashed. "What were you four thinking? Setting a dangerous explosives off the train!"
"We didn't mean for it to go off on the train."
Her nostrils flared and lips flattened into a thin line. "I suppose you were waiting for a better time." They said nothing. "I must say, I am very disappointed in all of you! Though I am not surprised by your involvement, Misters Potter and Black, I expected better consideration of not only your own but others' safety from you, Mister Lupin, and Mister Pettigrew I hope this will teach you to think before following your friend into folly. I am ashamed that the perpetrators of this act of destruction are my house!" Her ire released, satisfactorily to bow all; their heads in shame, she took a steadying breath and continued. "As for your punishment-"
"Professor," Remus interrupted and went on, unfazed by McGonagall's withering glare, "seeing as there was no permanent damage done to the compartment…"
Emboldened by this start, Peter picked up, "and nobody was hurt…"
"And we didn't mean for it to go off…" Sirius finished.
"Tha, I'm afraid, will not save you all from fulfilling punishment for the fiasco." McGonagall answered the unspoken question sternly as ever, but she had softened slightly under their pleas and they all knew that punishment would be less than originally planned. "Additionally, for your actions, Gryffindor House-"
"Professor," James, finally speaking, interrupted. "SInce term hadn't actually started when the firework blew up in our faces, you don't really have to take points from Gryffindor."
She scrutinized the bespectacled, dark haired boy as she considered his reasoning. After a long moment she nodded. "Very well Mr. Potter, I shall not take points away. However, all of you will serve two Saturdays detentions in my classroom, and I warn you, no more fireworks displays this year or I will take extreme action. Now, all of you up to your dormitory and get cleaned up." When they opened their mouths to question, she continued. "You will not come down for the Feast. I will not have the entire school congratulating you four! Dinner will be waiting for you in the tower." She paused, waiting for sign of their understanding, an eyebrow raised in expectation. Four heads nodded. "You may go."
After scurrying out before she could change her mind, they hurried for the tower. "Nice one, James!" Sirius admired, slapping his friend on the back.
"Not too bad, all things considered, only two detentions." Remus commented.
"Sirius, do you think you could recreate that wonderful invention of yours?" James asked, the glimmer of plotting alive in his hazel eyes.
"Absolutely!"
"But-" Peter began, McGonagall's scolding fresh in his ears, remembering the ban that had been placed upon them.
"For next year!" James elaborated. They all laughed, still bearing the marks of this day's misadventure.
