The Secret of Glendunny tells the story of a colony of beavers, or castors, who have been hiding, almost in plain sight, for five hundred years. Their safety and livelihood—timber—depends on their not being discovered. Humans have destroyed the ecology of so many of their fellow creatures' habitats that they will doubtless do the same for the castors. Added to that, the ruling council of the castors knows that their homeland hides a terrible secret: one that has been buried for centuries, and that no one must know. The trouble begins when one young castor, young Dunwattle, is disturbed by what he thinks is a ghost. In his panic, he strays far from the den, where he is discovered—and photographed!—by a two-legs (a human). As soon as the council learns of this, they are determined to get the lynxes to "take out" Dunwattle—but what they don't know is that Dunwattle's best friend, Locksley, is just as determined to save him.