Voorloper — Andre Norton

VOOR: A new planet, declared free and open to settlers by Survey testers; a wild but fertile land, dotted with impenetrable brush and lonely wastelands that remain unexplored, where frontiersmen had hoped to carve out new lives for their families. But a Shadow stalks on Voor, striking without warning at isolated settlements, killing nearly all, and leaving Shadow-touched and forever strange those few who are left alive. Now an oddly-matched trio has set out to learn the secret of the Shadow Death, heading deeper into the wastelands than anyone has ever gone: an embittered wanderer and his son, and a young girl who bears a Healer's gifts. All are Shadow-touched; what they had to lose is lost already; they are free now to risk their lives in search of truth