Miss Helen Shaw of Boston, New England, is delighted to learn she has become an heiress. The inheritance of her grandfather's house in the Connecticut mountains, together with a half-share in his prosperous ironworks nearby, means he has finally forgiven her mother's impetuous runaway marriage. She sets out to claim her new property only to find that even in the enlightened days following the American Civil War, sinister superstitions still linger amongst the mountain folk. For they call St. Thomas's Mountain -- site of the ironworks -- Satan's Mountain -- because they believe that Helen's cousin and fellow-heir, Robert Warren, is in league with the devil. And how can Helen disagree with this belief when the saturnine Robert is clearly determined to be her implacable enemy?