The Fade Away rule has been put into place to allow players to abstain from situations that make them uncomfortable without compromising their character's ideals.
Fade Away can be used when you accidently happen upon a scene that you would feel uncomfortable getting involved in, either by walking in on it, by scrying it, or by being contacted by another character.
You cannot use Fade Away in scenes that you are already a part of, or to avoid the consequences of your own actions. In these cases, see <help fade to black>. You cannot use Fade Away to avoid RP in general.
A character who invokes the Fade Away rule, announces this to the room either by say, emote or on the OOC line. They immediately leave the vicinity of the scene and ignore (and forget) its existence. Other players ignore the character and can continue their scene. The invoking character should not return to the area where the scene is taking place until it is resolved.