The Dragon's Secret by Augusta Huiell Seaman

Sixteen year old Leslie Crane has come to the New Jersey shore as a companion to ailing Aunt Marcia, whose doctor has sent her there for a 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. Little does she realize that she will not only soon make a new friend, but that they will both end up in the midst of a puzzling mystery centered around the closed up bungalow next door. Augusta Huiell Seaman is the author of over 40 historical fiction and mystery novels for older children most of which are currently out of print. The Dragon’s Secret was originally published in 1921.