1.. The alchemist turns up after you got the quest "find the alchemist" from the chieftain's son. Do you have this quest? It's connected in a linear way to "cause of the plague"
2. Cut scene at the rock in the south part of the Fire Area comes after you have found the alchemist and got the quest "cure for the plague"
http://beyond.divinedivinity.net/help/act2_forest_so.htm Here is a map link from Hellfighter => number 1 shows the alchemist cave in the Fire Area.
3. Key => it unlocks a chest in the spider area - SW bay. Nr 16 on the map Hellfighter made.
http://beyond.divinedivinity.net/help/act2_forest_no.htm
