Frank creates a car but when it begins to pollute Dinotopia, Mayor Waldo bans it. Frank, out of revenge, runs for mayor and wins, and allows the car to continue. However Frank soon learns the error of his ways, and resigns, allowing Waldo to return to his job.

The theft of a dinosaur egg during a special celebration sparks an incident with the Outsiders and Le Sage when it's discovered a dinosaur egg has been switched with that of a T-Rex, which hatches and wreaks havoc at the dinosaur nursery.

Karl finds a lost civilization within Dinotopia, who have never even heard of Dinotopia.

Karl discovers a radio in a wrecked ship and manages to get it to work, dreaming of using it as a way to leave Dinotopia. However, no one else agrees with him. Then the radio picks up a distress call from an outside world.

While trying to decide whether to return to their modern world, Karl, David and Frank must make even tougher decisions: will Marion go with them and who is plotting Dinotopia's downfall?