It is the second half of Stanley's journey which turns it into an epic feat of exploration. From Lake Tanganyika, where he had found Livingstone several years earlier, he and his diminished band of porters, including some rebellious ones who start the trip in chains, trek westward into the interior for some weeks, until they reach a large river, known locally as the Lualaba. No European explorer has ever gone downstream beyond this point, and no one knows where the Lualaba leads. Livingstone had thought it was the long-sought source of the Nile, since the Lualaba here flows north, straight toward Egypt.