The Corpse Thief

The Priests of Arkay are charged among other things with funeral rites and the proper burial of the dead. But lately, bodies have gone missing from the chapel morgue. The local priest suspected grave robbers, but many of the bodies were from common stock, with no jewels, treasure, or precious possessions of any kind. The priest will complain that the Guardsmen have already claimed to be looking into it, but it’s been weeks and no news. Any help would be welcome at this point. He will beseech the players to find out who or what is behind the thefts. This investigation will be complicated as the players will encounter a Necromancer, who will sic more than a few of these stolen corpses onto the players as undead, as a diversion for his own escape. The players will have to fight them off and track him down. They then can decide whether to bring him to the town guard for justice, or deliver it unto him themselves.
If the players deliver justice themselves and slay the Necromancer, then the quest is over; neat clean and pretty straightforward. If they deliver him to the Alderman for justice, then he will be arrested, tried, and hanged. Again pretty straightforward. However, in a few weeks, strange undead will be spotted in the woods on the outskirts of town. These undead will be just like the ones the players fought in pursuit of the Necromancer, those made of common folk. However, they will somehow be immune to any and all anti-Undead Restoration Spells, such as Sunfire or Turn Undead. Destruction spells will still work. These undead should appear periodically, until the players realize that the case was not so straightforward after all...