When a mysterious illness begins to spread among wild dragons, the children are charged with delivering a strange book, the Liber Draconis, to Dr. Drake, which they believe may contain a recipe for the cure. Travelling on the fabled Dragon Express, they cross many continents, befriend a colourful collection of new dragon species and escape from the clutches of the evil Alexandra Gorynytchka for a second time. But will they reach Dr. Drake in time? The future of dragonkind hangs in the balance.