In my campaign one of the characters is being followed so...
The PC is the son of a king. The son has never felt like a part of the family. He has always favored learning to be a musician and historian as opposed to his brothers, who study swordsmanship and similar activities. His father does not approve.
The PC sneaked away and is traveling under an assumed name so that he can live the way he wants to but he's certain that he's being followed. He's a bard class-wise, and earns meals and board as a traveling musician.
In this era in my campaign world demihuman races are almost extinct following a genocide and anyone found to be harboring them would be in deep stuff. The PC's father, the king, has allowed a few large populations of elves to live in the local wilderness unmolested, a kindness that would cost him dearly if it were discovered.
The PC (who thinks his father is a tyrant towards his family and subjects alike) has discovered he is being followed and believes that his father has sent assassins to kill him in order to preserve the family honor and keep him from revealing the family's secrets.
The facts are that the king's power is being eroded by the local barons, who are plotting against him hoping to seize his power. The recent years have been hard for the king, so he has tried to be harder. Fearing that an attempt to overthrow his family's rule was fast approaching, he took every effort to have his sons trained in battle and strategy. The PC resisted much to the king's dismay. When the PC slipped away the king became afraid that not only would his son's disappearance be seen as a weakness in the family, but that the young man would be killed by his enemies.
The possibility that his son would reveal their harboring of elves and bring destruction upon them in the process had occurred to him as well; his son being something of an impetuous, short-sighted and self righteous brat... He has sent some people loyal to him to find the PC but not to kill him, only to collect him and bring him back into the fold before he's killed or causes calamity to befall them.
In short; the PC is a runaway noble who is being followed by the king's agents so they can bring him back to his family.
Alternately, the king's enemies could have discovered the PC's identity and want to capture and either kill him, or pump him for information.
Edit:
BadMojo said:
Given the ability to easily magically impersonate anyone, down to the most minute physical detail, the mistaken identity thing isn't so bad an idea.
...
You could have it be some grand conspiracy, or just simply a crime of opportunity. Bad guy sees the PC in the wrong place at the wrong time, just some stranger on the street and BAM!, frames him.
I like that. What if some guy wants a particular thing, and makes a deal with a devil for it but the catch is that he's figured out how to get out of his end of the bargain. He also wants to stick it to the PC (for whatever reason) and disguises himself, through magic, as the PC. Disguised, he makes the deal, then makes a discrete exit leaving the unwitting PC to pay the demon.
Hehe. The funny part is finding out if the party tries to slay the demon (it is evil after all) or if they try to reason with it in order to resolve the matter. It could be the demon doesn't care who pays up, as long as it gets paid; on the other hand the demon, once convinced that it has been tricked, might get angry and agree to let the party off the hook as long as they find the jerk that dared to fool him. No one likes being tricked.
