The Road to Paradise Island — Victoria Holt

A SEALED ROOM. A MYSTERIOUS MAP. A DEAD GIRL'S DESPERATELY PENNED JOURNAL...
FOR ANNALICE, THEY LEAD TO DISCOVERY -- AND DANGER....

Annalice Mallory, sheltered daughter of a family of mapmakers, is thrown into a world of intrigue and high adventure when she discovers the cryptic diary of her long-dead ancestor. Along with the diary is a map of a mysterious, far-off island.

Philip, Annaliee's brother, is fascinated by the island's promise of incomparable riches, and leaves in search of it. But months pass without a word from Philip. And Annalice, determined to learn the secrets of the diary and desperate to find her brother, begins a journey that leads her through the world's most exotic outposts -- Cape Town... the Australian outback... finally to the lush, tropical islands of the South Seas..

There, Annalice encounters heartstopping peril... but also the promise of love.