OK let me get this straight: you freed Hendak, Hendak killed Lehtinan, then he asked you to clear out the slaver stockade and you did this?
Then the only thing I can think of is: have you freed the three children in the Slaver's Stockade?
BTW next time please put Spoiler in your post, yes, there are still people who haven't played the game yet and will be spoiled by this.
Good luck!
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Melusine
Your voice is ambrosia