When found, Willa is crying over the madness that consumed her family in their unlife, and upon talking to her, say she can hear them digging without end. She will then beg the Nephalem to release the Rathes from their torment. If a follower is present, they will say that Willa is telling the truth. This will initiate The Family of Rathe event.
Killing all three family members will allow Willa to be at peace as well.