After Capt. Haddock and Tintin invite an abused Roma community to camp on the grounds of Marlinspike, things get still more complicated when Bianca Castafiore and her entourage arrive as well.
When Bianca Castafiore's prized jewel disappears, the Roma camped on the grounds of Marlinspike are suspected while Tintin secretly investigates the situation.
Tintin and Captain Haddock have been asked to be part of the expedition to the moon. As they help Professor Calculus prepare for the launch, Tintin persists in finding the internal spy.
Tintin, Captain Haddock, Calculus, the Thompsons' and Wolff uncover the wonders of the moon. They also discover another person aboard the rocket ship who threatens to leave them all stranded on the moon.