Finn is fascinated by the idea of space travel. He longs to fly to the moon in a rocket to meet the man-in-the-moon face to face. So he goes to New York to meet the famous rocket scientist, Dr Gass, in the hope that the will realise his dream. But Dr Gass tells him the moon is made of rock, not cheese, and that there is definitely no man-in-the-moon. On top of everything, he won't even tell Finn where he keeps his rockets. Fin is bitterly disappointed, until he meets the Night Thing, who invites him to the man-in-the-moon's birthday party. Could Dr Gass be wrong after all? And how will he get there? In a rocket, of course, and the rocket is on the roof .