Just some run-notes from when I've run it (3 times now):
I made it a big deal just to try to get across the river into stromdorf. I had a LOT more reik eels and had the players chewed to ribbons.
I added 3 more NPCs so that the obvious bad guy wouldn't be so obvious. This is also one of the things taht I l like about the enemy within campaign. Have several NPCs very interested in their business. They can be commoners, nobles, or hell even a nosy blacksmith.
Try to throw out a lot more rumors about the locations and maybe add a couple more locations (I recommend 3) that are actually mundane, but then don't look like "Hey guys, here's the three locations we need to go to and hey, here's the 1 bad guy, because who else could it be?)
I actually try to always create at least 3 names of peasants who are the local gossips or suspects and have them doing things that are completely unrelated to the plot: "Did you know that mary has a really bad relationship with her mother and her mother in law died of mysterious circumstances?" "Did you know that ol' norskie's fishing boat is said to be haunted?" "Did you know that little ralphie pulls reik eels out of the river and maims them and puts them in his mother's bed..there's just something not right with that boy..or why would he do that anyways?"