DAUGHTER of Charles VI of France and sister to Charles VII; younger sister of Isabelle, widow of the deposed and murdered Richard II of England; wife of England's Henry V; mother of Henry VI; secret wife of Owen Tudor and grandmother of Henry VII; princess, pawn, woman of power, prisoner - Katherine of France (1401-1437) was all these. ``The Queen's Secret,'' by Jean Plaidy, is her fictional autobiography. Though the daughter of a king, Katherine did not have the pampered upbringing our imaginations tell us she should have had. Instead, she and her siblings lived in near poverty with their insane father in the H^otel de St-Paul, while her unscrupulous mother ruled - many would say ruined - France. By the time Katherine was in her teens, Richard II of England had been deposed by Henry IV and murdered; his widow, her sister, had returned to France and remarried; two of her brothers had died, possibly at the hand of her mother; and France was in the grip of civil war, with conspiracies lurking at every corner.
By the time she was in her mid-20s, Katherine's life resembled the overambitious plot of an overzealous amateur's 19th-century opera. Henry V conquered France and she married him. Their son was born, but Henry V died suddenly. Joan of Arc reunited the French against the invading English. And Katherine had secretly borne to Owen Tudor - her clerk of wardrobe - two sons, whom she left in England while she accompanied her first-born - now King Henry VI - to France. There, among other things, Katherine witnessed the martyrdom of Joan of Arc by the English.