Bess Marvin won a five-day vacation in the Bahamas and invited Nancy Drew and George Fayne to go with her. Before Nancy arrives at the resort, Bess is kidnapped, and the only way to save her is to solve a 300-year-old Bahamian mystery. Dangerous waters keep treasure hunters from exploring the reefs around Dread Isle, but this remote island might hide the riches of El Toro's lost fleet of seven ships. Can Nancy track down the treasure before time runs out?