The series is based on the journalistic material by Lawrence Wright, "Rex Cobb and the Cowboy Mafia," published in Texas Monthly in the early 80s. It tells the story of hidden treasures that hold the secrets of a real crime. The Kingdom of North Texas is divided into two parts. Many knew Rex Cobb as a successful entrepreneur, farmer, and poker player. However, soon his name became associated with smuggling illegal substances... and oil.