A farmlady in Phandalin tells Willow and Kal that people has been moving away from Thundertree because people started to get sick and started to die. It seems to have come from the forest?
Reidoth/Reidolph the druid is currently at Thundertree.
There are "human trees", called twigblight, they are usually only dangerous if provoked.
Willowbark notices it is the same kind of disease that plagues her forest, and is determined to find out what is causing it