Thelma witnesses a UFO sighting in the sky over Wamurzelles and encounters a mysterious investigator. Axelle is promised a promotion if she can ensure the smooth running of the grand musical chairs competition at the autumn festival, a competition that Micheline and Jeanine are working tirelessly to organize.

Axelle's promotion is jeopardized following Micheline's disappearance; she must find her, but her investigation is stalling. Thelma and Steven run around the village collecting testimonies about the UFO and eventually find Billy.

Axelle questions Billy but can't help harboring doubts about his guilt. Thelma persists in her investigation with Steven, but their frantic search for evidence will lead them to go a bit too far.