sentences:  The "Mushroom Planet," visited by the protagonists David and Chuck, is covered in various types of mushrooms and is populated by little green people.The story opens with Theo Bass, the cousin of Tyco Bass, coming to Pacific Grove, California, and visiting the two boys (Chuck and David) from the first book.He has been a traveler around the world for many years, and when he finds out about the mushroom planet, he decides to rebuild the boys' lost spaceship and return to what he knows is his ancestral home.