Returning to the Castle of Moulinsart of his previous adventure, Tintin and Captain Haddock learn that Professor Calculus Silvestre has gone Syldavia. After meeting with him in the Balkan country discover that Calculus is working on a secret atomic research facility in the heart of the mountains of Zmylpathes. The teacher has been hired by the government to direct the construction syldavo an atomic rocket board which will make the first manned trip to the moon.
From there the whole adventure unfolds in the space station and the surrounding mountains. Assist the construction of the rocket (which resembles a German V2), the first tests and his own training as astronauts (little intense for what will be the real astronauts training years later). At the same time, must contend with a mysterious plot, apparently led by the neighboring Borduria, which aims to sabotage the project. The ineffable Thompson and Thomson are sent to help with investigations.
Finally, despite the difficulties, the rocket is ready and off to your destination. That stops the weft, which will continue in the next volume: Landing on the Moon.