I'd be interested in your notes on Book 3: The Harvest of Sorrows.  

We started out adventure last weekend with the arena adventure from the book.  There escape was made possible by a priest of the yellow druids.  He intentionally kept that a secret for obvious reasons.  All he asked for in return was for them to fetch a magical item from a rival sorcerer of his masters.  Most of all he said was a lie, because he actually wants it for himself to give the yellow druids an extra edge.  The sorcerer in question resides in the Elephant Tower(this will pretty much follow the storyline of the book with a few modifications so it fits our plot line). 

I think this story line of yours might be a good fit for the situation they're in with the yellow druid.  Particularly, because the arena they were in was in Lysor and their success may make them somewhat responsible for the madness which the druids end up spreading.

There's nothing like letting players think they're not doing anything that bad.  Only to have them learn the hard way that they did something really bad.  It'll be suprisingly easy with this group.  They all took Taciturn as a flaw.  So they didn't ask the druid many questions.  Or any questions for that matter.