Title: Trixie Belden and the Mysterious Code
Subtitle: #7
Description: When the Bobwhites take a week-long vacation on Cobbett's Island they find that their vacation house has a hidden story. Will the Bobwhites be able to solve the mystery before it's too late?

Linked book is actually Mystery on Cobbett's Island, as per the cover pic, not The Mysterious Code as in the title.
Subjects: Trixie Belden (Fictitious character), Detective and mystery stories, Ciphers, Fiction, Clubs, Mystery and detective stories, Children's fiction, Belden, trixie (fictitious character), fiction
People: Trixie Belden