Skyhorse

Judge Nathan Berkley requests a seemingly simple task of his adopted son, Appaloosa King: ride to the remote town of Deadlock to pick up Catherine, the judge's newly-discovered daughter. Trouble starts when, on the way, King leads his two cowboys off on a diversion, aiming to meet up with a mysterious messenger - who, unbeknownst to the trio, has a deadly reason for the rendezvous. All looks lost until a stranger arrives on the scene - the man known as Skyhorse...
Skyhorse by John Ladd