The Idylls of the Queen is set in the Britain of King Arthur, as portrayed by Sir Thomas Malory's classic Le Morte D'Arthur; as specifically stated by the author, no attempt is made at depicting with historical accuracy the time of the actual King Arthur.
It expands an incident in Malory, in which the Queen is accused of murder, into a complex mystery novel mingling the genres of historical mysteries, Arthurian legend and fantasy.