Another message, the single word "Grun" sends Jack Coughlin, Collin, and Danny back to The Hidden Moon and a fight for their lives!
Jack Coughlin's magical stone from Anron sends another Morse Code message. This time Grun, the name of the evil creature they all thought was gone. Jack, his brother, Collin, and their friend, Danny, return to outer space to help their Anronite friends, Karna and Nidar. Grun, the enemy of the People of Light, is very much alive and is determined to rule The Hidden Moon for his own. The battles to save Anron from Grun's control take the boys from the dark side of the moon to the dangerous Bogg on nearby Planet IXX where they must risk their lives to win the freedom to go back home again.
Trouble on The Hidden Moon is the third in the children's Hidden Moon Series, another book by J.S. Keim, filled with fantasy, fun, and danger.