...Well, that's about fifty kinds of suspicious.
"Hey, Giles," she says after school, a flyer torn on one corner from where she was uncautious about pulling it from its staple, "does this all-caps warning here look fifty kinds of suspicious to you?"
"Do you suppose Sunnydale High has some known problem with people going stag to prom mysteriously dying or otherwise suffering nasty fates that I should fix?"
"I don't know where records of prom deaths might live. My first idea was to figure out who wrote the flyer and figure out where they got their info."
"Alrighty. Prom's not for a while, so no huge rush." Pause. "Although if I'm going, I have to invite Sherlock - lest I be killed by the Phantom of the Promenade before having a fighting chance - and I have to find a dress and so on. Or I'll just be turned away at the door and the inevitable poor sap who ignores the all-caps warning will die."
"If it's anything sillier than a prom ghost I fear that will be its actual weapon, it will silly people to death," snorts Juliet.
Sally Williams is organizing prom. Sally is uncomfortable about explaining the warning, but ultimately confirms that, yeah, people who go stag or even with a group of friends? They keep turning up dead. So this year they're just forbidding single attendance.
And how did they die? Bella wants to know.
Sally Williams doesn't know.
Bella goes to the library and reports to Giles. "How do I figure out what it is?" she asks, spreading her hands.
"Does it drown only boys there? For that matter, who does it strangle? The flyer forbids both sexes to go stag, but the prom organizer doesn't have a lot of details, she just knows there's something to be afraid of."
"If it only drowned them, I'd wonder if it was some kind of - I dunno, despair spirit, provoking loneliness to the point of oddly specific suicide, but if it strangles people too I think it must have some more physical presence," opines Bella, "am I wrong?"
"You think it's a ghost, then, not a demon? Naively I would guess a ghost would be more likely to be preoccupied with the love lives of high school students."
"Okay. So the ghost is substantial enough to strangle people, but is it also substantial enough that it will care if I kick it in the head?"
"If it doesn't care about being kicked in the head, will it care about getting torched? I don't have great wand control yet, but I think I could refrain from burning down the school, and then I'd have a chance of not needing to use squares. Or, I could go straight to the squares, but what do I wish for, what process do I disrupt to rid us of Prom Ghost?"
"Mightn't it just recoalesce? It's already making trouble only during prom - once annually - as far as we know. It's pretty low-key, and it wouldn't be immediately obvious if I'd only spooked it into leaving for a relatively meaningless period of time." Pause. "Heh. Spooked."