I'm gming a Pathfinder game. It's part hack-and-slash and part detective work/mystery solving. The premise is that there is a young necromancer raising the dead to right a wrong. Now, the source book states she is not evil per se, but moreso insane, but she is still a necromancer.
The twist of the whole game is that the characters are living almost on top of this girl without knowing that she is the one.
But how do I handle this mystery of "who is behind the whole thing" when basically my Paladin can go "Okay, I detect evil on the group ... oh, okay, yep, there she is - evil, for certain!"?
Okay, for clarification, as requested:
I'm playing a D20 adventure called "The witchfire trilogy".
The premise of the game is that Alexia (the girl from the cover) was as a child witness to the beheading of her mother (and several other women), a witch in her own right. Her mother was originally not evil but was set up and forced into doing more and more evil things, which eventually lead to her beheading. Alexia is now coming of age and is finding suddenly great necromantic powers awakening in herself. Since she is sure that her mother was innocent she starts going around and raises the dead jurors of the trial as zombies and skeletons, so she can question them, trying to find out who was behind it all. Her intention is not evil at it's base, and the sourcebook literally states "Alexia is not evil, she is just misunderstood", but come on - she creates skeletons and zombies, which is necromancy, which is, as I understand it, evil by definition.
So, right at this moment my main question revolves around "Detect evil", which several of my players can do with their characters, but the larger question remains: how can one play a mystery adventure when powerful wizards or clerics in good standings with their gods have great clairvoyance spells that basically allow them to look things up?
Of course I could give the "bad guys" some ring or other, but it feels very weak as a solution.