To cut it short, the players (it's a 3 people party) are in some kind of a Secret Service of a rebel prince who wants the throne. One of my players is working for the current king secretly, feeding him info, sabotaging the missions he gets from the rebel prince (like accidentally shooting a VIP he is supposed to protect), etc. The other two doesn't know about it both in-game and out-game.
We use the bathroom when I have to tell a player something secret. But if this player keeps playing the double agent for longer, I will be spending half of the game in the bathroom and the other players will get paranoid and these guys just can't stop themselves from metagaming. I mean, imagine 4 people (3 PC and 1 NPC) sleeping in a room and waking up with the NPC dead. You would be suspicious of the guy that DM always secretly talks to, right? I know the players will eventually find out, but I want to keep it secret as long as I can.
Whad'ya suggest? Can't think of anything myself, other than learning telepathy. Just give up and give a lecture on the evils of metagaming maybe? I thought about making up an excuse to talk to all players in the bathroom during stuff like the assassination example above so everyone will be suspicious of each other but it sounds like too much hurdle.
Please note that 2 of my players are Evil and all of them have things that they keep secret from each other, which leads to a lot of bathroom-talks.