 After defeating a rival railroad company and laying track to supply the US Cavalry near the Mexican border, Amelia meets a French prospector named Pierre Beaumont, who helps her and US Cavalry commander, Major Cooper, defeat a Mexican army attacking a fort. He then lures Amelia to a mine in Colorado where a surprise visit from an aged Kanyenke, who has brought Cooper and the cavalry with him, reveals Beaumont as the leader of Circle of Ossus. Amelia, Kanyenke, and Cooper chase Beaumont through the mines, where they find a map to the Lake of the Moon.
