Human bulldozers are digging up large sections of Parc Montsouris and are getting closer to the mouse village. Pamplemousse encourages the villagers to move, but Anatole thinks they should first find out why the bulldozers are digging so much. The sight of the bulldozers and the destruction they cause, bothers Claude so much that he begins to have fears and nightmares about a dragon (that looks suspiciously like a bulldozer). As half the town pack to leave, Anatole learns that the humans are digging randomly in search of a major underground pipe leak.

With the help of his friend Moliere and Mole, he discovers the leak's location and conveys the information to the humans. Saving the village, as Doucette helps Claude realizes that his irrational fear of a dragon is based upon something real, and once you know what you are afraid of, you can overcome it.