Accompanied by her seaman uncle, Charles Cap, Mabel Dunham travels toward Fort Oswego, on Lake Ontario, to visit there her father, a sergeant major in the British 55th Regiment. They are guided through the wilderness by a Tuscarora (Iroquois) named Arrowhead, who is accompanied by his wife, Dew-of-June. En route they come upon the camp of Natty Bumppo (the guide and scout now known as Pathfinder) and his adopted brother Chingachgook (Great Serpent), both sent as additional protection for Mabel and Cap as the French and Indian War flares up sporadically along the northern edges of the British colonies. With the scout and his Delaware companion is their friend Jasper Western, a young freshwater sailor on the "inland sea" (Lake Ontario).