Chiana Ryan, PI (sort of), is deep in the middle of an exciting mystery, and everything is coming up eggs. First there's the 120-million-year-old dinosaur egg that disappears from its stand at the museum. Then there's the shed full of eggs she stumbles across while investigating crazy Professor T. Goodenough's scary signs.What do these eggs have in common? What are the strange creatures hatching from the eggs in Professor Goodenough's shed? And how can Chiana find time to follow clues when the owner of Treehaven Riding School keeps her busy riding and looking after the horses? Chiana and her friends are determined to crack the case, even when the clues bring them to the egg thieves themselves. Suddenly, it's horses against motor bikes in a desperate race for survival...