RB-105 The Falling Giants

Something is wrong, very wrong, with the giant pines in the national forest. The giant pines, some over 100 years old, are falling down for no apparent reason. Bill must close all the roads and trails through the giant pines. Scientists can't find anything wrong with the trees. Bill and Henry must go back into the giant pines to uncover the problem. Will the fellas be able to dig up the reason for the falling giants? Or will Bill lose the giant pines to this mysterious ailment?