The Happy Hollisters and the Cowboy Mystery (#20 in the Happy Hollisters series)"Domingo," the burro the Hollisters were given for a pet the last time they were out West, is the innocent means by which the Hollisters once again find themselves following the mystery trail on horseback.Because of a near accident the Hollister children meet and befriend the Blairs, who are from Nevada. They learn that Mr. Blair is trying to sell some of his property...