Balthazar and Jumbo are two secondary school students. This year, their French language teacher asked them to write a fictional story. Without hesitation, the two students chose a comic strip to portray events involving creatures from outer space. During a visit to the observatory, Balthazar encounters Agent Muller, a mysterious scientist who falsified research conducted by the young space scientist Paola Dell Aqua.
Paola disappeared without a trace. Thus they carry out an investigation and discover that Agent Muller was behind her disappearance. Paula will be freed, and the two young heroes win a prize for their story.