In a small southern seaside town live two faithful friends—Stas and Vlad. They dream of becoming real sailors. During summer vacation they spend all day on the shore near the ruins of an ancient half-destroyed fortress, which, as before, hides many secrets. The boys imagine they were cast away on an uninhabited island after a shipwreck and arrange their life like real Robinsons. Trying to unravel the mystery of the old fortress, the boys discover a terrorists’ cache…