The Dragon's Secret - Augusta Huiell Seaman

Sixteen-year-old Leslie has come to the New Jersey shore as a companion to her ailing Aunt Marcia, whose doctor has sent her there for some quiet rest and recuperation. While the beach is lovely in October, Leslie quickly finds herself getting lonely with no one her own age to talk to. But one day, her dog digs up a metal box with an engraved dragon on it. This will lead Leslie not only to a mystery but also to a new friend.