The story of Diana Budisavljevic, who embarked on a campaign of rescuing more than 10,000 children from the Ustasha camps in Nazi-occupied Croatia. A dramatized retelling mixed with archival material and interviews with survivors.

Koko and his friends are spending summer vacation on the shores of a lake near the idyllic Green Hill, hanging out and playing. 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, stealing anything valuable they can find. 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.