"I solemnly swear that I am up to no good."
Fred and George had carried concealed broomsticks at all times since the previous year's troll attack. When they heard Harry Potter's prophecy at the Quidditch final they flew just over the castle walls and then Apparated to the graveyard where they salvaged their map along with several rings, amulets and strange devices.
"Have you visited every room on this map?" Luna asked.
"Excuse me?" George said.
"What part of the school have you never visited?" Luna enunciated each word.
"Did she just insult us?" Fred said.
"Perhaps our reputation is in disrepair," George said.
"What makes you think there exists a single room in the school we hadn't explored by the end of our first year?" Fred said.
"Are you telling me you visited every room in Hogwarts in your first year?" Luna said.
"We make no such claim," George said, "For if were we to make such a claim then we would include not just mere rooms but also secret passages, pocket dimensions, secret dimensions, pocket passages, and docket sassages."
"Surely someone of your reputation must have visited every room, passage, dimension, sassage and chamber by the end of your first year," Luna said.
"Surely," Fred said.
"Had you visited the Chamber of Secrets before Headmistress McGonagall announced its existence today?" Luna said.
Someone said a rude word.
"Where is the Chamber of Secrets?" Luna asked.
"It's this complex of tunnels," George said, "It connects to this painting of Salazar Slytherin to this girls' bathroom and these places over here. This path goes to the Hogsmeade graveyard."
"Has the Chamber of Secrets always been on this map?" Luna asked.
"Yes," Fred said.
"How do you know?" Luna asked.
"I remember it," Fred said, "I just never really noticed it before McGonagall's announcement."
"Are there any other rooms on this map you haven't noticed?" Luna asked.
The students failed to find anything they hadn't found before.
"I have an idea," Luna said, "First we are going to look at this map normally. We are going to list every room and secret passage we know of, including the Chamber of Secrets. We are going to count them. Then you are going to conjure a grid over this map. We are going to count every single room without identifying them. Then we will compare the two numbers."
The two numbers came up exactly the same.
"Wait a minute. I have another idea. Give me that list. Is there any room in this castle you haven't been to?" Luna said.
"No," George said, "We've been everywhere important except the Chamber of Secrets."
"Let's go over the map again," Luna said, "List each room you've been inside."
"…and that's the broom closet we trapped Percy in along with his girlfriend, his ex-girlfriend, his ex-ex-girlfriend and Peeves," Fred finished.
Luna tore up little bits of parchment and covered up each room Fred and George had visited. She had covered nearly all of the Marauder's Map. There were just a few unimportant rooms that didn't really count. Then Luna caught herself. This must be what a Muggle-Repelling Charm felt like.
Luna deliberately read off the unimportant rooms she had just nearly written off.
The room of requirement canonically does not appear on the Marauder's map.In fact the Marauder's map has no reason to show the Chamber of Secret since if it is supposed to show only places that the Marauders know (I don't remember what is the origin of the map in HPMOR though).
Harry speculates that the marauders stole part of the Hogwarts security system, but he's not necessarily a reliable narrator.
Other fics imply that the map might have read-only access to the Hogwarts Wards/wardstone, in which case the Chamber would not have been there until the wards were adjusted to allow entry.
This and the previous post have surprisingly few comments but a sufficient number of upvotes to post it somewhere more fac-fictiony. Or is this intentional?
I'm a bit surprised the twins had the patience and concentration to sit with Luna and help her go over the map over and over.
I think what happened is the Wesley twins noticed that they had contradictory beliefs:
Thus they know for a fact that something about the map is fucking with their memory or perception. Hence "Someone said a rude word."
They might not ordinarily have such patience, but Luna's appeal to their pride should've helped. Plus this involves the Weasley twins telling tales of their escapades, which they surely enjoy.
This bit bothered me too, it's pretty out-of-character for them. I think they'd indulge her going over it once, but not twice or thrice, so it'd be better if @lsusr rewrote this chapter to add some reactions of theirs and some reason they'd accept it, and her managing to figure it out after that one single attempt.
One option might be her figuring out one smaller-ish thing at her first attempt, let's say, the Chamber of Secrets, making them excited. Then drop the second attempt, moving straight to the third attempt, where the two truly secret areas are revealed, and adding their reaction at this.
Maybe she reminds them of Harry.
I like this idea. Maybe she could even say something in particular that reminds them?
Especially as no character has given a reason to suspect any sort of "perception filter" a la Doctor Who. Incidentally, didn't Hogwarts often reconfigure itself in HPMOR? Seems odd, then, that Fred/George believe they've seen it all.
In parts 1 and 2 Luna is shown as being at the same time a paranoid conspiracy theorist, as well as a skeptic, and someone possessing, for whatever reason, a natural resistance to perception filters, all of these traits combining into making her into someone who questions everything and everyone, even if that questioning tends to look pretty random to everyone else. Therefore, it seems to me pretty reasonable for her to question the truthfulness of the map, as it looks a little bit too convenient, a little bit too easy, for a paranoid who takes to heart the notion the best place to hide is in plain sight, to accept. Those with that inclination tend to think "What better way to hide the top secrets if not by making available carefully curated lesser secrets that will redirect curious folk away from the truly important secrets?", witness QAnon, and therefore go after the presumed true secrets.
What's distinctive in this case is that Luna's paranoia is actually merited, and leads to the actual uncovering of actual deeper secrets behind the shallow, distraction secrets.
Which fits with her canon counterpart. ↩︎
It wouldn't surprise me if, differently from her canon counterpart, this Luna were able to see thestrals despite never having seen someone die. I'd like to suggest @lsusr to change chapter 1 slightly to refer to her mother as still alive. Those who remember from the books she's able to see thestrals because she saw her mother die in a magic accident will then wonder. ↩︎