In 1757 the French around Montreal are poised to move south. A young American volunteer in the British Army, Sergeant Tom Cutler, is sent northwards carrying a dispatch which orders the garrison of Fort Williams to reinforce the vulnerable Crown Point outpost. Cutler is murdered on the way by two men acting as British scouts, one of whom is an Ogane, a French-allied Huron posing as a Mohawk. Crown Point is not relieved in time and falls to the French
Returning home after two years away, Sergeant Cutler's elder brother Nat "Hawkeye" Cutler and his companion, a Delaware Indian Chief Sagamore, investigate the killing of Tom, who is now wrongly believed to have been a traitor by the authorities. Nat and Sagamore enlist as scouts for the reinforcements being sent out to Fort Williams. They escort the British Captain West carrying important despatches, and Marion Thorne, the daughter of the Fort's commander. They foil an attempt by Ogane to betray them to the Hurons and bring them safety to Fort Williams. However, their apparent insubordination leaves their commander's suspicious of their loyalty.
General Montcalm is being supplied with information by a spy inside the Fort, which is carried out to him by Ogane. Montcalm ambushes a force of American infantry and advances with the French Army to lay siege to the Fort. Hawkeye is able to expose the traitor as Captain Brownwell, a French-born officer serving as quartermaster to the British forces, but is too late to stop further information passing out to Montcalm. Aware that the Fort is indefensible, Montcalm offers it favorable peace terms. This outrages Ogane who wants vengeance against the Anglo-Americans, and he leads his Hurons in a night attack in which they kill many of the Fort's defenders. Marion Thorne is kidnapped by Ogane who wants her as his wife.
Hawkeye, Captain West and Sagamore follow the Hurons and rescue Marion. They are then pursued by Ogane until they reach the shelter of the Ottawa tribe, rivals of the Hurons. The Ottawa leader suggests they can go free if one of them can defeat Ogane in single combat. Hawkeye fights and kills Ogane, and they are allowed to return home. Hawkeye is appointed as chief scout to the British forces as they prepare a fresh offensive for the following year.
