For their summer holidays, three students — Alja, Žana, and Simona — decide to take a canoe trip down the Kolpa river, the river which divides Slovenia from Croatia. They are unaware that they are being watched by the Guardian of the Frontier, a conservative local politician, the self-styled defender of traditional Slovenian values, who is quite possible prepared to kill those who transgress.

As the girls float deeper into the woods, cracks develop in the three girls’ relationship. Is there more than friendship between Alja and Žana? Does Simona harbor a secret sympathy for the Guardian and what he stands for?

With nowhere to turn, the three girls must decide: what is a border crossing and what is just an imaginary line?