Mia and Felix Fox join a supervised boat survey to investigate why a mysterious Star Island appears on an old sea chart but not on a newer one. By comparing maps, following natural landmarks and exploring carefully with a harbour researcher and Dolly Dolphin, they rediscover the hidden island and help record it on an updated chart. An exciting exploration story that teaches map reading, observation, comparing information, safe exploration, and understanding that one source may not always contain the complete picture.