I've got a scenario about half written, but I'm having some problems.
Situation: Strange occurrences, including the dead rising from their graves.
Cause: A mad necromancer has stumbled across a map drawn on enchanted paper. At one point in the past, the paper was used to create powerful scrying aids. The necromancer is obsessed with the map, and spends hours studying it. He's loosing control of his faculties, however, and sometimes casts spells without realizing it. Due to the nature of the map, whatever he casts is directed at the location of the map, as if he is there in person. Sometimes this results in the dead being raised, sometimes he causes fear and nightmares in the townspeople who happen to be at the target area.
My problem is this: How on earth are my players going to discover this?
They'll hear through gossip and rumors of the problems around town, and will most likely hunt down any undead that they hear of. I'm just drawing a blank on how they're going to be able to connect the problems with the cause.