This last volume recounts the expedition's experiences as they continued their journey homeward from present-day Idaho and the party divided for separate exploration. Lewis probed the northern extent of the Louisiana Purchase on the Marias River, while Clark traveled southeast toward the Yellowstone to explore the river and make contact with local Indians. Lewis's party suffered from bad luck: they encountered grizzlies, horse thieves, and the expedition's only violent encounter with Native inhabitants, the Piegan Blackfeet. Lewis was also wounded in a hunting accident. The two parties eventually reunited below the mouth of the Yellowstone and arrived back in St. Louis to a triumphal welcome in September 1806.