During a summer holiday, two boys discover an anti-gravity cannon in an old attic.
A German family Keller arrives to the coastal village to spend summer holidays with their Croatian friends. Horst Keller and Roger Katushic were friends ever since Karl May's film adaptations took place there. Their children were friends for years, too, and they look forward to the reunion. Fantasizing about free life and "cowboys & Indians" adventures in the canyon of the Cetina river, the boys go there without knowing that the three cruel Chetniks who had just escaped from prison hide there.
After Italian capitulation in WW2, German forces are rushing to take control of the Dalmatian coast, forcing thousands of people to take refuge. One partisan boat, filled with refugees, tries to reach a safe area, but because of a storm it must stop near a small island. While the crew tries to repair it, a German gunboat comes from nearby.
