First, on the second visit to the cave, you need to play cat and mouse with "The Law."
Then, you have to wait a month near "Andragor," or spend about a month running around, and if you enter the cave three times, "that friend" will be there again. :)
In the end, I spent about 12-13 days in prison.
As for the breakthrough, it involves running to the "mentor" and into the "peaceful" cave. There are also advantages; I was already level 37 (+ 2 skill trees and a quest that gave me an almost unbeatable 40) on my 6-7 month (Veteran Mage) playthrough, but then I still had to gather some more troops for the mausoleum. The map was completed in 204 days.
Also, I'm thinking of playing Heroes of Might and Magic: The Eastern Expedition this weekend.