All noise ceased in the dungeon classroom as the 4th year Gryffindors and Slytherins turned at the sound of the door opening. In swept Severus Snape, fashionably late, cloak billowing in an unseen wind, potion master, 'reformed' death eater and bane of all Gryffindors to have ever walked the halls of Hogwarts. At least that was the plan.

Before anyone could react and before an even semi impressive billow could be coaxed out of his cloak Severus Snape was caught by a trip jinx and sent crashing to the floor.

Everyone was in shock as they watched their potions professor fall, seemingly in slow motion, to the floor. That wasn't all, as the floor didn't seem to stop him. He just kept right on going, through the floor and out of sight.

The Slytherins were outraged. The Gryffindors were torn between outright joy and trepidation at the punishment sure to come their way.

Professor Trelawney's class of 3rd years were interpreting their dream diarys. It had been an unfulfilling lesson for most of them, especially for Luna Lovegood whose mother had already taught her practically all the useful aspects of divination, being a seer herself. She was half listening as Professor Trelawney told the girl next to her that very soon a tall dark man would appear very prominently in her life and to watch for him.

She was pulled out of her reverie by the sudden appearance of Professor Snape approximately seven feet directly above their table and travelling towards them at high velocity.

There was a deafening crash as he hit the table, almost drowned out by an even more deafening shriek from Professor Trelawney, who promptly fainted.

Professor Snape rose groggily, everyone in the class could feel waves of hatred, rage and contempt emanating from the man. They didn't need a seer to tell them that someone was about to need a new school, if not serious medical attention.

Standing straighter Snape stalked out of the classroom without a word.

Luna turned to the girl next to her, who was white with shock and fright, and said sweetly; "You don't think he was the tall, dark man for you to watch out for do you?"

The girl went even whiter, if that were possible, before fainting like her teacher. Luna giggled inwardly whilst humming a tune and skipping out of the classroom with her books.

Snape raced through the castle back down to the dungeons. He banished the trip jinx on the door with a wave of his wand, cast a finite spell at the invisible portal on the floor and stalked into the classroom ready to string up every Gryffindor in sight. At least, that was the plan.

He did successfully removed the trip jinx, but unfortunately missed the muggle trip-wire that it concealed. His finite spell did manage to get rid of the invisibility part of the portal but as to the portal itself, all it achieved was to change its destination.

Professor Flitwick's class was having a brilliant time. They had been taught the summoning and banishment spells and were currently using them to have a rather large scale pillow fight. Professor Flitwick was refereeing with a smile on his face. He'd always believed that learning should be fun and so was permanently trying to come up with new ways to enhance his lessons with such activities. The fact that it drove everyone to master the charms as quickly as possible was always a nice bonus.

Currently the Ravenclaws were winning, having taken an early lead what with the majority getting the hang of the spell faster than their Slytherin counterparts. The Slytherins were slowly clawing their way back with underhanded tactics, however.

It was into this fun and chaotic mess that Severus Snape appeared, falling at considerable speed. If he was surprised that his forward momentum had once more been turned into downwards momentum, he was even more shocked that said downwards motion was once more converted into horizontal motion by application of a banishment charm.

Astoria Greengrass was having a wonderful charms lesson. She'd quickly picked up the banishment charm and had yet to resort to the cheating tactics of her housemates in order to start gaining the upper hand. Her aim was still a little off though. Her fun was quickly turned to shock and horror as her housemaster appeared in front of her, even more so as one of her misaimed spells struck him square in the chest and sent him flying at full speed through the closed window with a loud crash.

Suddenly everyone stopped what they were doing. There was a seconds pause before they all, Flitwick included rushed to the window in time to see a screaming Professor Snape cast a cushioning charm on the ground and slow his descent nearly four floors and forty feet from where they were watching. Still in shock, Professor Flitwick turned to Astoria once the potions professor had run inside the castle. "I won't tell him if you don't" he said to the girl, who looked like she was about to be sick.

Professor Snape's eye was twitching in rage as he rant full speed towards his classroom. He decided 'To hell with subtlety' and leapt over the tripwire in his doorframe and, with a shout of triumph, over the visible, two foot wide portal on the floor.

Unfortunately he missed the, still invisible, vertical portal just beyond the one on the floor.

Dumbledore was having a bad day. The board of governors was not impressed with how the Triwizard tournament was going so far. An escaping dragon was a sure fire way to have bureaucrats and parents alike screaming down his ear. He was just finishing up the meeting, feeling slightly worse for wear when he sensed a peculiar brand of magic in the air. He pulled out his wand and looked suspiciously at the governors arranged in front of him.

He was very surprised, though he tried not to show it, when his potions master came flying out of the portrait of Dilys Derwent to land just behind the governors' chairs.

"Ha HA!" he yelled triumphantly as he arrived, before landing awkwardly and taking stock of the situation. As Dumbledore and the board turned to face him he went very red in the face, a vein on his forehead began to pulse ominously and his right eye began twitching like mad. Without another word he turned and practically ran from the room. The board of governors quickly turned back to Dumbledore.

"Albus, wasn't that man Professor Snape?" one inquired

"Why yes I believe he was."

"Shouldn't he be teaching right now?" another asked

"That was my general impression of today's timetable, though I could be mistaken."

"Then what was he doing appearing in your office? I thought apparition was impossible on the grounds."

"I can assure you I have no idea why he was here, or indeed why he left so abruptly, though I have my suspicions. As to your other question, it is quite impossible to apparate here without my lifting the wards to allow it. I assure you that once we are finished here I shall devote my best efforts to unravel this mystery" the aged headmaster replied with a twinkle in his eye.

It was several hours later as Harry was sat in the Gryffindor common room that the secret behind Professor Snape's vanishing act came out. Fred and George had just wandered in and sat by him busy congratulating themselves.

"Why Gred, I do believe that this was our best prank yet."

"Indeed Forge, though I do think we owe it to our little house elf friends more than we'd care to admit."

"Yes, but it was spectacular wasn't it?"

"Indeed it was, oh brother mine."

"Go on then, spill it," Harry said, taking the bait, the twins always loved bragging about their exploits to him, he thought they might be trying to groom him into their protege or something, "It was you two who set up that thing in Snape's dungeon wasn't it?"

"Whatever do you mean Harry?" said one

"You couldn't possibly be accusing us now could you?" said the other in a hurt tone

"Cut it out, what did you do?"

"Ah, well, you know how the house elves can pop about here there and everywhere inside the castle even though apparition is impossible."

"Yeah"

"Well, we've spent the last three years getting all buddy-buddy with them down in the kitchens and we finally managed to persuade them to teach us how they do it."

"So you can now just pop about wherever you want? That's amazing!"

"Whoa, not so fast there, cowboy. It may be an innate skill for house elves but for wizards it takes an incredibly complex and difficult spell to even get close to matching the results."

"Yeah, you have to set up portals and arrival and departure wards, it's just not practical for everyday use."

"However, with a bit of Weasley tweaking…"

"We could, say, set up an entry portal somewhere…"

"Make it invisible…"

"Key it in to a specific person…"

"Then set up exit portals in several key locations around Hogwarts…"

"Not to mention the surrounding grounds and forest."

Harry was in awe, these two were geniuses. "Wait, how many exit portals did you make?"

"Let's see…" they began to count off on each others fingers

"Well one in each of the other teachers' classrooms and offices…" one began

"In case a certain someone wanted to visit his colleagues." the other justified with a grin

"Then their's Dumbledore's office…"

"In case they have a report to give, or a detention to justify."

"Draco Malfoy's bed…"

"Because sometimes we all just want to visit our favourite student."

"The great lake…"

"For bath time"

"The Three Broomsticks…"

"Somewhere to go to wind down after a long day's cruelty."

"The Acromantula den, the centaur sleeping quarters, the unicorn herd's glade, the threstral feeding gourds, the mermen underwater city and Charlie's dragon enclosure in Romania."

"In case they wanted to collect some rare and exciting potions ingredients." They finished with an evil grin.

"Oh and Professor Sprout's manure heap out behind greenhouse two."

"Oh, yeah, I forgot about that one… did we ever come up with a justification for that one?"

"Why no, brother mine, I don't believe we did."

"Ah, well, you win some, you lose some… right, I'm off to bed. Pleasant dreams Harry."

"Yeah, see ya Harry."

They both left, still smirking at the gobsmacked teen they had left in the common room.

Harry's dreams that night were very pleasant indeed, seeming to involve, for no apparent reason, a certain potions master in several life threatening situations.