The "trailer" is a dog named Caesar and the killer is a mountain lion, aka as a cougar or puma the narrator was quick to point out.
Burgess and Greeley are rustling horses and shooting Indians. When they kill Manual they frame Lieutenant Allister. His older brother John now attempts to defend him at his murder trial.
Kildare kills Curt Fremont's brother Jim. When Curt arrives he poses as a coward in public but sneaks out unseen to become the daring El Capitan as he looks for the killer.
