I have a situation. My group is heading towards an elven kingdom in pursuit of a plot coupon. Unbeknownst to them, the plot coupon is evil and corrupted and is turning the royal elven family paranoid, seeing plots in every corner. One of the player characters, unbeknownst to everyone (both in- and out-of-character, even her player) is a member of this royal family, so as soon as they enter the country she should start to fall under the effect.
I'm looking for ways to engender a feeling of paranoia around the table – I've thought of passing secret, DM-eyes-only notes about and making significant glances, but I'm really reaching for ideas here (since I think they'd cause more player- than character-paranoia), especially since the whole point is that the other players' characters really aren't plotting anything, just trying to save the king and his family from the madness, Secret Elven Princess just thinks they are.
I certainly don't want real-life, why-is-my-friend-of-five-years-plotting-against-me paranoia, but I'm trying to achieve the in-character sense of irrational mistrust due to outside influence despite there being no in-game justification for it.
There's a whole bunch of character backstory stunning plot twists that are going to fall out of this, so I want it to be good.
TL;DR: How do I make a player think other players' characters are plotting against her character without them actually plotting anything at all?
Best Answer
I agree with you and with other commenters that inducing out-of-character paranoia is a really bad idea and would not be fun for your player. Anything you do needs to make it clear to your player that the other players are not actually conspiring against her.
If you want a specifically in-character effect, and not out-of-character paranoia: just tell her that her character is feeling irrationally paranoid, and ask her to roleplay that for a bit.
You could say that in private or you could say it publicly at the table; I recommend the public option to minimize OOC tension.
If you like, you could offer experience bonuses for working it into the narrative. (Either just for the paranoid character, or for others as well for cooperating.)
If the above doesn't work for you, another option is to narrate flavor onto player characters' actions.
(later)
By doing things in this way, you make it clear that the players aren't actually doing any conspiring. The risk is that the players might notice you doing this, and might try to "help" you by narrating their characters doing suspicious-looking things. You might have to directly ask them not to do that.
If your group is into mechanical penalties, you could assign those as well. Maybe allies now count as flankers, or maybe she has to roll will saves vs friendly spells if they happen by surprise.