This entry contains the first part of the audiobook "Stopinje po zraku" (Footsteps in the air) by author Leopold Suhodolčan (COBISS ID: 273202947, ISBN: 978-961-7194-59-3).

The detective assignment that catches Naočnik and Očalnik on vacation somewhere between Vogel and the Triglav Lakes Valley is this: to solve the case of the flying saucers that has caused enormous panic among holidaymakers and people in general. It turns out that Earth has been visited by an expedition from the distant planet Mirion. More precisely: aboard the interplanetary spacecraft White Ray are the Mirionian detectives Naoč Nik and Očal Nik, who look strikingly similar to the Earth detectives Naočnik and Očalnik. Their mission is to find the first expedition that came to Earth in search of a planet with which they could share their technological achievements and inventions for the benefit of humankind. The crew of the first expedition disappeared without a trace, and Naoč Nik and Očal Nik have come to ask Naočnik and Očalnik for help in the search.