When her absent-minded inventor father suddenly remembers that he has five sisters, nine-year-old Harriet Bean, who has never heard of them before, determines to find her unknown aunts so that the unfinished family portrait can be completed.
En route to a small island in the Caribbean, the school ship Tobermory encounters modern-day pirates, and twins Ben and Fee MacTavish must use their wits to escape harm and overcome the evildoers.
"When two siblings attend an unusual school, aboard a ship, they make new friends, learn about all things nautical, and become involved in a mystery they feel compelled to help solve"--