11-year-old Michael sets off with his family on a journey around the world. When a storm breaks out on their way, the boy and his dog are thrown overboard. They wake up on a tropical island that seems deserted. However, Michael soon discovers that it is inhabited by one man - Kensuke. This World War II veteran is taciturn, avoids ships, and approaches the boy with distance. Soon, dangerous poachers appear on the island. Will the castaways manage to establish a thread of understanding and find a common language to save their secret world?