Islands in the Mist breathes new life into ancient Welsh mythology, masterfully weaving its characters into a rich tapestry of heroism and sacrifice.

The great warrior Bran has been called home from the battlefield to his mother's deathbed, where he vows to solve the strange mystery surrounding what fatally attacked her in the night. He travels to the Crossroads, seeking the wise counsel of Talhaiarn, high priest and advisor to his clan, where he learns similar attacks have been reported by clans to the north and east—horrors that Talhaiarn determines are the dark handiwork of the powerful Cerridwen, a rogue priestess of the sisterhood that dwells on an island surrounded by the misty waters of Lake Tegid.

On his journey Bran encounters the fiery, red-haired Lucia, widow to a Roman centurion, and her strangely gifted stable boy, Gwion, an enigmatic child graced with understanding far beyond his years. Lucia possesses "the Sight", an ability that has plagued her from the time she was a small girl, tormenting her with visions of terrible things that invariably come to pass. Fate leads Lucia to discover that many of her maternal ancestors were masterful women gifted with psychic abilities, and some of them have been watching her from the shadows for years.

Upon returning to his village, Bran finds himself at odds with the hot-tempered Aelhaearn, who is determined to become their clan's next chieftain. Much to Aelhaearn's disappointment, Bran's sister, now priestess in her mother's place, convinces the clan to choose Bran for the honor instead.

In the aftermath of their conflict, Bran learns something shocking about his rival. Slowly all are pulled into the seductive maelstrom of Cerridwen's power, and though many will fight bravely, only one is able to make the sacrifice required to defeat her.