With his father gone to fight for the South, Boone McCallister and the "cow hunters" of the Flat Iron Ranch drive 3,000 head of scrawny cattle to a Gulf port south of Tampa, dodging Yankees as well as a degenerate bunch of swamp outlaws, the Klees. Boone is an appealing young man, mature and immature at once. Congratulating himself on getting Cuban gold for his cattle, rather than Southern scrip, he runs into some callow Yankees and orders them hanged. The Yankees killed one of his men, and war sentiments run high, but the hanging proves a bad omen when the Klees raid the Flat Iron and steal a comely young slave, Lena. Boone braves vengeful Yankees, water moccasins, and alligators to force a showdown in the outlaw camp that was to become Miami.