The Ambassador’s bodyguard quaked at the sight of the uniformed skeletons guarding the main gates of the royal palace. "Don’t be afraid," the Ambassador said. "They are King’s Bones, the monarch’s personal bodyguards, and are no threat to us unless we were to do something stupid like trying to attack His Majesty."
A plague has hit the local area.
In humans it affects only the most vulnerable, the children and the very old, and even than it's little more than a summer cold. 24 hours of sniffles and then it's gone, barely noticeable really.
To sheep however it is fatal and the whole economy of the area is in serious trouble. If this keeps up the area could well be facing famine.
Somebody (enter the PCs) must find the rare herbs needed to make a cure.