"You know," said Ginny Weasley, twisting a strand of red-purple hair round her finger, "there's something very strange about Luna."

"Since when hasn't there been?" Colin Creevey laughed between mouthfuls of Harry Potter's banana.

"No, I mean stranger than usual. I keep turning round and she's disappeared."

"Well, you know, you are a bit taller than she is. Maybe if you looked down slightly, you'd see her more easily."

"Shut up. No, she really does vanish. Wait a moment…"

"I'm sure she doesn't vanish. It's probably just your imagination. Although, now I come to think of it, we are in a school of witchcraft and wizardry, so maybe it wouldn't be so surprising. Ginny?"

There was no reply.

"Well look at that. Just me and you now, Mr. Banana, I suppose."

Harry Potter was searching under a cushion in his dormitory. He was looking for his banana, which had mysteriously disappeared during that lastDA meeting.

"Harry?" said a voice behind him, and he sprang up, rolled under the table and had his wand in his hand ready for action before the owner could say another word.

"Oh, it's you, Ginny. Sorry, just a bit jumpy, what with this Transfiguration exam coming up and having to defeat the Dark Lord."

Ginny privately decided that Harry had some issues. "Harry, I don't suppose I could sneak a look at that map that my brother's gave you? The Marauder's Map?"

"What map? I don't know of any map of that name! Are you sure that you heard correctly? You couldn't be asking the wrong person, could you? Oh, sorry. Old reflexes, you know how it is."

Ginny, who could no longer go into a bathroom without a wand at the ready and who at the mention of the word "snake" couldn't help shouting out "can't say I've ever seen one, must be someone else you're thinking of", "I can remember where I am at all times, thank you very much" and "the Dark Lord is so not controlling me", smiled slightly. "It must be hard. So could I have a look at it?"

"The map? Sure, here it is."

He handed the map over to her and she sat down on the bed, looking over it with extreme care. "Found what you were looking for?"

"No. Harry, have you ever heard of someone being in Hogwarts but not showing up on the map?"

"No, I think it pretty much shows everyone."

"Then I think we have to go and see Dumbledore. Now.