S1, E40: Fumé asks his son to watch over the water plant while he's away. Grisù accepts this mission and Stella comes along. But the young dragon accidently pulls the wrong lever, causing the water to heat too much. To cool it down, Grisù and Stella have to turn a wheel but they end up getting it unhinged. Fortunately Grisù and Stella manage to press a red button, which is a like a second line of defence.