Basic outline:
- Somewhat-obsessive lawkeeper goes after a mostly-turned-evil character (non-PC)
- said character captures the lawkeeper, torturing him for a bit before letting him go (like I said, mostly evil, but still with a prohibition against killing)
- the lawmaker captures said character and dumps her straight into prison without trial (mind you, by this point she hasn't done anything worse than associating with criminals and the tortue of him), and, as he was head of that prison, took advantage of it to torture her considerably
- she escapes and finds asylum elsewhere (eg. the group the PCs associate with, very LN and "don't bother us and we won't ask questions")
- the lawkeeper follows, gets killed, and comes back as a ghost haunting the character (admittedly slightly convolutedly, since it won't actually come near her)
By this point, she's been pretty well messed up by it, and the only way to completely reassure her (she's needed for other story bits going on) is to have her destroy the ghost herself. This is what leads to the problem, since it won't actually manifest near her, so ghost touch weapons, for example, are more or less out of the question-- plus, she has some sort of magical effect on her or mental block (I'm not sure) that's keeping her from directly seeing it if/when it does manifest... (Admittedly, this might carry over if it's made incorporeal, but it's worth giving a shot...)