"Flay them alive... boiling oil..." Argus Filch mumbled as he stepped out of his office. He'd just brought those smirking twins in there-- at least he'd caught them, this time, when they charmed the toilets -- and he was about to give them a really excellent punishment -- really excellent, mind you, not any of the normal cleaning trophies, oh no, not for those two -- but Peeves was throwing mudballs in Snape's dungeon, and that was rather more important at the moment. He slammed the door behind him as he left, Mrs. Norris snaking around his ankles.
        As soon as he rounded the corner, the door to his office squeaked open again. A shock of red hair poked out into the hallway, swung back and forth once, and then popped back in.
        George grinned at his brother. "We're clear. Filch and his sweetheart won't be back for a while."
        Fred had already started opening drawers and rifling through file folders. "Good of old Peeves, eh? We've been wanting to get into this place--"
        "--since Charlie told us about Filch--"
        "--and how he's an uptight old git." George was looking now, too, picking up a sock that was enchanted to smell ten times worse than bubotuber pus. At least, he hoped it was enchanted. Disgusted, he threw it back down. "I reckon there's loads of things we could use in here," he said.
        Fred looked up, holding the non-business end of a fanged frisbee. "Right, but we don't have a lot of--"
        "--time, I know. What do you say we do?" Fred examined the walls.
        "We-ell, he does have that list, you know..." The two of them turned toward the wall next to the doorway. Many sheets of parchment, some cracking and curling with age, others that looked as if they had just been placed there that day (and they probably had-- George noticed that Tummy Tumble Jam was near the end, and they had only perfected that last week) were tacked from the ceiling to the floor, overlapping each other, listing in Filch's deliberate, miniscule scrawl the three hundred and sixty-two items that were officially banned at Hogwarts. Filch had done his homework: next to the name of each item was a short but complete description of exactly why it was banned. It was as good a place to start as any.
        Fred pointed to an entry and grinned. "Fang earrings. I guess that's not in the uniform, is it?"
        But George was looking elsewhere. "Wall-dissolving binoculars, sneeze-inducing feather dusters... none of this is quite as useful as I'd hoped." He skimmed down the list, automatically skipping anything that they already had in their trunks, when his eye caught on a phrase. "Enchanted map of grounds," he said thoughtfully.
        "But Hogwarts is Unplottable, dingbat," Fred said, pushing his brother out of the way so he could examine the entry.
        "No, it isn't-- just hard to find, that's all. Besides, a map of the grounds wouldn't tell you where Hogwarts was, it'd just tell you where you were when you're inside it. Now give me a hand; I want to find this thing." They started examining the cabinets, flipping through folders to see if they could figure out where it might be. It didn't take them long to find out-- in the big bottom drawer of Filch's desk there was an oversized padlocked briefcase that said in large print "ENCHANTED DOCUMENTS."
        George pulled out his wand. "Alohomora." The lock fell out of its loop and George pulled out a stack of papers. Most of them were silly game pages that girls made up: write your name on the line and the parchment would tell you which one of the boys you liked was going to kiss you, how many times, if you'd get married, all that rubbish. One of the documents was a drawing-- it showed you an caricature of yourself in an embarrassing situation. "I'd like to see the look on Percy's face if he found this in his Transfiguration textbook," he said, showing it to Fred. The last paper in the briefcase looked as if it had been stuck there so it wouldn't be found; meaning, of course, that it was a sure thing that anyone who wanted it would.
        "This is it," said George. Fred agreed. It was folded like a map, even though there was no text on it, and it had, well, a mischievous air about it.
        Fred pulled his wand out and tapped the parchment, saying, "Okay, map, show us what you've got." Ink swelled up to the surface of the paper.
        "Messrs. Moony, Wormtail, Padfoot, and Prongs would like Messrs. Fred and George Weasley to know that Messrs. Weasley appear to have got a horrible disease with skin lesions all over their faces and that we hope it worsens." The brothers both chuckled. This was their kind of map.
        "Thanks, blokes, we know. Messrs. Fred and George Weasley would like you to know that we intend to use this map for only the best purposes. Like sneaking around under Filch's nose."
        "Do you swear?"
        "We do."
        "Do you solemnly swear that you're up to no good?"
        "Of course we solemnly swear that we're up to no good!" George practically shouted this, and Fred brought a finger to his lips. They only had another minute or two.
        "Well, then, in that case..." And the ink on the parchment disappeared, and then began to appear in an entirely new configuration. The map worked! George quickly unfolded it to look at the corner of the castle they were currently occupying. "Look!" he said, pointing to the two dots in what was clearly labeled "Argus Filch's office". "That's--"
        "--Filch!" Fred said, grabbing the map and stuffing it into his robes. Sure enough, the door squeaked open and the greasy skull of Argus Filch swung into the office.
        "Peeves is gone. And Dumbledore wants you back in your tower. Says it's too late for detention." The man was positively fuming. Mrs. Norris hissed at the red-headed twins.
        "Right, then. Well, we'll--"
        "--be going now. Night, Mr. Filch, sir!" And Fred grabbed George's wrist and ran out into the hall.
        Filch looked around his office. Good. Everything looked just as he'd left it. Mrs. Norris was mewling,laying on top of a briefcase. "Yes, I agree. Time for dinner indeed."