Hi and welcome, Trinity <img src="/ubbthreads/images/graemlins/wave.gif" alt="" />
1. did you find out the cause for the plague? (Altoflix) - did you report this to the Chieftain's son? As soon as he gives you the quest to find the alchemist, you'll find him in the fire area, in his cave.

2. If you are in the cave => what does the minimap say? How many crosses are there? 2 for the plague victims and maybe 1 somewhere in the black?