''The Last Sin Eater'' is a story that takes place in 1850s Appalachia in a settlement community of Welsh Americans. Ten-year-old Cadi's grief over the death of her beloved grandmother, the only person who seemed to love her unconditionally, is compounded by a previous family tragedy for which she believes her family blames her. During her grandmother's funeral rites, Cadi sees the face of the village sin-eater, a person who absolves the deceased, at death, of their sins in this tiny Smoky Mountain community.