According to the npc at the sawmill at the middle of the night, lost men and supplies. Hints at otherworldly forces due to the suspicious screams. Suggested hang out night the mill..... I'm tired of waiting - no no... Who decided?
In short for those who have not had the spirit of thief and he was practical unthinkable amount of time waiting for supernatural. Go forward in the mine at the entrance of the robber. Send spirits to the light and turn in the quest to Galar.