So, back to plot advice in my Urban Fantasy high school setting. Magic is not known to the public at all. In the game so far we've glossed over the general public finding out by the PC's and NPC's just keeping as low a profile as possible, and there's been -hints- about a mage that has been keeping a 'don't worry about it' field on the city on the nonmagic populous.

But.

In a few sessions there's going to be a bit of a splash. An angry disciple of Bast is going to be turning an entire Homecoming Dance of teens into cats. They'll get turned back, and there is a teacher who has been shown to have the ability to memory-wipe a single kid in the past. Now I could say 'she uses up insane amounts of power and gets everyone who was there', but I feel that's a bit of a cheeseball cop-out. I -don't- want the kids to remember, as the 'keeping magic secret' is a major theme of the game. So, I'm looking for options. How do you make the big magic splash, then make those who witnessed / were touched by it forget about it?

(Possibly the cure for cat-dom involves rewinding time to the beginning of it? That, too, sounds a little deus-ex-machina-y...)

Convince the high schoolers that someone spiked the punch with something hallucinogenic?  That would have worked in my high school...

Then, have the teacher use her ability to make people forget across the entire student body at once and argue that diluting the power of the spell just makes the memory of the time in question fuzzy rather than forgotten.
This message was last edited by the user at 21:14, Wed 05 July 2017.

You could always just assume that the transformation itself wipes the memories of the night in question...and what doesn't get completely wiped is probably going to get covered by denial and the strong desire humans have to cling to a point of reference they feel comfortable with.

In other words, they don't remember anything their cat-brain experienced and if they did odds are that they'd suppress it on their own.  Not exactly a (mentally) healthy outcome but very likely.  If anyone has to he brainwiped, it'd be the kids with very adaptable minds who might be a possible ally or threat.

A combination of things? The teacher expands her power to make things fuzzy, which combines with the fact that the kids remember strange smells and sights rather than the actual transformation, and the whole thing gets explained away with 'someone spiked the punch with LSD/psilocybin/Hallucinogen of choice'.

If it's a paradigm shifting plot point, you could start to suggest "higher powers" at work, enchantments, supernatural beings, or "natural laws" akin to Changeling's Mists or Werewolf's Delerium.

To avoid PCs abusing this sort of set dressing for their own personal gain, you may want to highlight some sort of karmic consequences for forcing this force/being/organization into action.

Maybe a little too WoD, maybe a little too much to wedge into your setting, but any modern hidden magic setting mileau needs more than a few grains of handwavium, pun intended.

Edit:

Could be some kind of Dementor-like demon beast who consumes the residue of magic from non-magic users, and sucks their memories along with it, and which uses those memories to hunt down magic users and consume their magic (and their miiiinds!)  Like some kind of mnemonic Langoliers.
This message was last edited by the user at 21:40, Wed 05 July 2017.

Given a physical transformation, I would say that everyone involved retains hazy, drunken memories of being cats, but that their fragile human minds are working overtime to make all occurrences fit into a human context in their minds. That guy who, as a cat, had to mark everything as his territory? Yeah, he just remembers a wild night of street art and graffiti. Scratching every available surface? Just a bunch of riotous teenage hooligans out on the town. And so on, every imaginable cat behavior translates in the memory to an analogous human behavior, everyone assumes that their memory is hazy and surreal because the punch was spiked, and anyone who wants to tell crazy cat stories must have been on something a lot stronger than alcohol.

There's also a useful narrative tool that is already there in myth (and was a major plot element on the Percy Jackson books due to its connection to Greco-Roman myth): Mist.

Effectively, when the human world brushes up heavily against the supernatural world in a way it cannot comprehend, it actively refuses to see what is real, and adjusts accordingly. The thought being that massive events happen all the time, but we simply don't se them, or remember en masse differently to remain sane. That battle between god-like entities? Hurricanes.

I'm sure someone brought this up but I'll simply reiterate.   People tend to dismiss what they can't explain and/or understand.   A very easy explanation is "Nah, didn't happen."

Overlapping with the above, there's the "all just a dream" explanation.

Isaac Asimov (I think) once wrote a story exploring how people would rather deny their senses than admit something impossible (the protagonist could fly), and it was only when the protagonist demonstrated his power and then denied it that he got people to investigate it (because no-one truly likes to believe they've gone insane, which was the other explanation). I suspect this is true. and we'd latch on to any 'rational' explanation rather than admit we'd seen something impossible.

Psychological studies have shown that people are very suggestible, even if they think they're not (e.g. they'll describe a target's eye colour if asked, especially if prompted, even if the target was wearing dark glasses; one false witness can corrupt the memories of a number of real witnesses so they'll claim to have seen something they didn't; etc). Although we often think of memories as being a recording of something that happened, they're constructed more than recorded. (I realised this when I recalled a scene from my childhood... and realised I'd given all the buses the colour scheme of a bus I was familiar with rather than the one that would have actually applied at the time :)

So a single persuasive speaker (or magic) could easily convince (most) people they hadn't seen what they saw. On a darker note, this is one approach to propaganda: repeat a false statement often enough, and even people who ought to know it's false will start to believe it.

This also leaves open a plot-hook of the one person who won't be persuaded.

What about the chaperones? Did they see the transformation or were they caught in it? Maybe those are the memories the magical teacher most needs to change.

And did the tuxedos and gowns transform? Or did we end up with a gym full of empty formal wear and a bunch of naked teenagers?

Finally, what about that feline behavior that leads to feral colonies all over town? Will there be unexplainable consequences in nine months? Will that be different to the results of previous proms?

What will work is whatever the players will accept. I would ask them. Maybe they're fine with a cheese-ball cop-out. Maybe they'll come up with an idea that everyone here who isn't a player in your game would reject. They might reject any idea that anyone else comes up with anyway.

As long as it isn't specifically integral to the implementation of the forget it all... let the players vote for one of a few options, and even encourage them to tweak one some, or volunteer a new ideas their fellow players can choose to vote for.

You don't have to give them all the details, in case, for instance you don't want them to know who the teacher is who might potentially be the reset-or, or don't want to explain the full nature of the magic.

For instance, whatever enabled the person to change all the teenagers into Cats, may have 'modified' the nature of magic in the building, such that it allowed the 'forget' to affect everyone.  The example being, normally, the person who changed everyone to cats, may have only been able to change them one at a time, but by using some sort of focus, perhaps they were able to trigger a 'expanded effect' metamagic field with allowed a single target to be spread within the space for a certain amount of time, which the other teacher may have been able to leverage, once they determined what that focus was, and targeted his magic through it.  The focus however might have been unstable, so may have consumed itself, or it might have been dependent on external factors.  (astrological convergences, etc.)  So it need not be a sudden permanent concern or imbalance factor.