Soon after Anna Pigeon joins the famed wolf study team of Isle Royale National Park in the middle of Lake Superior, the wolf packs begin to behave in peculiar ways. Giant wolf prints are found, and Anna spies the form of a great wolf from a surveillance plane. When a female member of the team is savaged, Anna is convinced they are being stalked, and what was once a beautiful, idyllic refuge becomes a place of unnatural occurrences and danger beyond the ordinary.