After a successful surgery in the U.S., Zuzia returns home with her parents. During her absence, Lampo – her beloved Swiss Shepherd, known nationwide as the “Railway Dog” – is left in the care of the station master. The orderly life of the man who agreed to take the dog under his wing soon turns into chaos. Despite occasional mischief, Lampo still loves riding trains. One day, however, he doesn’t return from his travels as expected. His GPS tracker offers no clues, and the trail goes cold. In a panic, the station master decides to adopt a Swiss Shepherd from a shelter to cover up Lampo’s disappearance. However, when Zuzia arrives back home, she immediately notices the dog at the station is not her Lampo. The new dog is a female named Luna! Together with her friend Antek and her furry new companion, Zuzia embarks on an adventurous journey to solve the mystery of Lampo’s disappearance. Naturally, the panicked station master is hot on their trail!