Return to Valbona

To find the answer, one must walk the edge of an abyss.
Three students from the Czech Republic go on a mountain hike in the Prokletije mountain range for vacation. And they disappear. Their families are inconsolable. The government, radio, and... television get involved in the search. But even Interpol does not find a trace of the young people.
A few years later, Jana receives an envelope containing the passport of her missing sister. Among the postal stamps, there is one that cannot be traced to any location on the map — Valbona 666. Is it possible that her sister is alive and sending a sign? Is it still possible to save her? Otherwise, who and why would need to send her passport?