In 1757, during the French and Indian War, British forces at Fort William Henry and Fort Edward in New York prepare for an imminent attack by French forces from the north. As the French forces, under the command of General Montcalm, and their Iroquois Indian allies move down from Canada, Magua, an Iroquois Indian scout serving the British, tells General Webb, the British commander at Fort Edward, that he has spotted Iroquois approaching from the south, not the north. Webb, who is expecting the arrival of the two daughters and young son of the commander at Fort Henry, General Alexander Munro, fears that the English visitors may have come under Iroquois attack en route to the fort, and sends troops to find them. Major Duncan Heywood, who is escorting Munro's daughters, Alice and Cora, and their brother Davy, arrive safely at camp a short time later. Hawk-Eye, a white scout, warns Webb that Magua, whom Munro had flogged earlier in the year, is a traitor and that he lied about the position of the attacking forces. Webb, however, refuses to believe that Magua is disloyal, and ignores Hawk-Eye's warning. The following day, Webb sends his men to the south to intercept the French and Indians before they attack, and arranges to have Cora, Alice and Davy sent north to be with their father at Fort Henry. Meanwhile, General Munro tries to warn Webb that the Iroquois are to the north of Fort Edward, but the Indian messenger carrying the warning is killed in an ambush en route to the fort. As Heywood and his charges travel northward, Hawk-Eye and his friend, the Mohican Chief Uncas, find the dead messenger and try to warn Heywood of the danger ahead. After Hawk-Eye wins the trust of Heywood, he is placed in charge of delivering the Munros to safety. Magua eventually reveals his true loyalties when he flees from the group during an Iroquois attack. Heywood chases Magua into a lake, where the two battle each other. When Magua and Heywood reach the shore, Magua's Iroquois compatriots surround Heywood and chase him back into the lake. Heywood swims to an island in the lake while Hawk-Eye wards off the Indians by shooting at them. The travelers rest in a cave on the island, and Hawk-Eye soon realizes that the Iroquois are planning to take Cora and Alice hostage. While guarding the Munros, Heywood is injured in the battle with some Iroquois warriors who have landed on the island, leaving only Hawk-Eye and Uncas to defend the group. Surrounded by Iroquois, Hawk-Eye devises a plan to trap the Iroquois by allowing them to capture Cora, Alice and Davy, and then following them to Magua's village. The scheme goes as planned when Magua abducts the Munros and Heywood, and takes them to his chief. At the Iroquois village, Uncas tells Magua's chief that the Munros are his prisoners, and that Magua stole them from him. When Davy sets off firecrackers to divert the Iroquois' attention, Hawk-Eye effects a daring rescue of Cora and Alice, and they continue their journey to Fort Henry. While crossing a hill, the travelers spot General Munro and his weary soldiers in the distance and race to meet them. Davy, Cora and Alice are reunited with their father, who has lost his fort to the Iroquois, and Magua and his warriors observe the reunion from afar. Sensing an imminent attack by the Iroquois, Hawk-Eye urges the British to circle their wagons and prepare for a gun battle. During the fierce Iroquois attack, Uncas kills Magua in a hand-to-hand battle, and then leads British reinforcements to the site of the battle. The reinforcements arrive in time to rout the Iroquois warriors, but Alice and Uncas are killed in the bloody battle.