Toma Serdarević

Koko and friends spend summer vacation on the shores of a lake near the idyllic Green Hill. The magical countryside is disturbed by unusual events which alarm the children as well as the locals: under cover of night, burglars break into one house after another. When the police turns a blind eye to denunciations by adults, the children decide to take matters into their own hands and unmask the burglars.

After discovering corruption among the school administration, three seniors and a freshman break into their high school to obtain evidence that would bring the perpetrators to light.