The Happy Hollisters and the Castle Rock Mystery (#23 in the Happy Hollisters series)An abandoned rock quarry, mysterious flying objects, and a valuable deposit of titanium lead the five Hollister children-Pete, Pam, Ricky, Holly, and Sue-into their latest thrilling adventure.When a package of instruments from a weather balloon is parachuted onto their front lawn, the Hollisters are baffled and very excited. Just what is the meaning of the orange...