After young orphan David Ritchie finds a new life in Kentucky, Col. George Rogers Clark enlists the boy in his daring quest to capture the Illinois Country from the British. Serving as Clark's drummer boy, David accompanies Clark and his intrepid volunteers on their arduous march across the prairies to Kaskaskia and through freezing swamps and backwaters to Vincennes. Years later, David has become a prosperous lawyer while Clark lives alone, forgotten and in poverty. Clark, in collusion with the French, hatches a desperate plan to regain his former glory by seizing control of the Mississippi from the Spanish. Unable to turn Clark aside from his plans, David and his roguish cousin Nick journey to the French settlements at St. Louis and New Orleans to thwart the scheme... and discover far more than they bargained for.