Bored with the Social world of London and the constant demands of the lovelorn Prince of Wales, the Marquis of Aldridge takes refuge at his remote country estate, Ridge Castle, deep in the 'Witch Country' of Essex. Riding through a village close to The Castle he comes upon a mob of villagers dragging the unconscious body of a young woman to the duck pond. Convinced she is a witch, they are bent on putting her to the ultimate test. If she drowns she is innocent. If she floats she is evil and must die! Rescuing the young waif and installing her at his castle, the Marquis is convinced that this raven-haired, blue-eyed beauty, whose name is Idylla, is far too lovely - too innocent - to be a witch. Nevertheless, he falls helplessly under her spell - and as he uncovers the murderous plot that brought her to him, he also discovers a love beyond anything he imagined possible.