Girl of High Adventure by L. T. Meade

Marguerite St. Juste was Irish on her mother's side, who was born of the Desmonds of Desmondstown in the County Kerry. Marguerite's father was a French Comte, whose grandfather had been one of the victims of the guillotine. Both her parents are dead and she is being brought up by an aunt and uncle. She wants to find out about the rest of her family and her adventures take her to Ireland and France. - Summary by Michele Eaton