After a successful surgery in the US, Zuzia (Liliana Zajbert) returns to Poland with her parents (Mateusz Damięcki and Monika Pikuła). During her absence, Lampo, the girl's beloved dog, known nationwide as PKPies, is placed under the care of the train station director (Adam Woronowicz). The orderly life of the man who agreed to take in the Swiss Shepherd turns into chaos and chaos. Despite his occasional mischief, Lampo still loves to ride trains. One day, however, he doesn't return from his journeys on time, and even a GPS tracker attached to his collar is of no help. The panicked director decides to adopt a dog of the same breed as Lampo from a shelter to prevent his disappearance from being discovered. When Zuzia returns to her hometown, she immediately realizes that the animal at the station is not her beloved dog, and what's more, it's a female named Luna. Together with their friend Antek and their new furry companion, they embark on an adventurous journey to solve the mystery of Lampo's disappearance. The panicked director, of course, follows them.