I was playing my non-violent mage (she has zero kills on her record, and generally runs to legion riders and guards to defeat enemies who must be killed.) She was doing the Mages Guild quest to get her staff, and had managed to sneak all the way through Wellspring Cave, and was attacked by the boss necromancer there. She ran all the way back through the cave, out onto the road, followed by the whole train of necromancers, zombies, and whatnot.
She has water-walking enchanted on her shoes, so she ran across the lake to the IC. The necromancers did not follow, but ran along the shoreline. My mage entered the IC through the Market district. Instantly, every guard in the Market district yelled "For the Empire!" and they all started running to Green Emperor Way. My mage went on around the city, by way of Arena, Arboretum, etc., and every time she entered a district, all the guards took off running. By the time she got to Talos Plaza, there was a horde of guards pouring through, and out the main gate.
They all ran off in a long column toward the south, swam the lake, and headed into the woods near Pell's Gate. That's where I gave up the chase; my mage wasn't fast enough to keep up with the running guards. As far as I know, they're running still.

The Necromancers never showed up. I had to load a save and start the quest over.