On a starry night, in the suggestive setting of the Gola del Bottaccione, Professor Albani gives an astronomy lesson to a small group of people, among them there are also Don Matteo, Pippo, Natalina and the Marshal. The next morning Albani was found lifeless at the bottom of the gorge. Some strange light phenomena, which occurred the night before make Pippo and Natalina begin to believe in the presence of UFOs.
