During the dark years of Oliver Cromwell and the Civil War, Blythe Brown, together with her brother Barnaby (children of a wealthy ship-owning Mercer) run wild during their childhood around the shipping port of King's Lynn with their Wolfhounds as protectors. Blythe, dressed in her brother's cast-off clothing, learns to sail, swim and swear, together with other useful abilities not normal for a girl of the 1600's.
It is clear to the local Wise Woman that Blythe is a natural psychic and clairvoyant, so teaches her the arts of healing and herbalism. When Blythe is eighteen, the Witch Finder General gallops into King's Lynn searching for witches. The son of a Bible-thumping Preacher, he despises women and seeks their undoing. When he spies the beautiful Blythe, he becomes obsessed - his desire is to get her into his clutches and to see her, ultimately, hanged.