In 1725, ten-year-old Cathleen Abigail Satterfield pleads with her father to allow her to become an officer in the navy, as her brother Piers has done. Her father, Richard, demands the girl conduct herself as a proper young lady destined for marriage and responsibility. Cathleen, known to most as Cat, is a clever and wilful child. She disguises herself as a boy and runs away from home to become a sailor in hope of finding adventure in faraway places...