Augusta Huiell Seaman 
The Girl Next Door [EPUB ebook] 

Marcia tells her friend Janet that the nearby house that always looks shuttered, dark and vacant is not so. There are people living in there. They learn that a young girl their age, Cicely Marlowe, lives there with an older woman who wears a veil over her face, Miss Benedict. They find out that Cicely does not know why, when her mother dies, she was sent to live with Mrs. Benedict. She was never told. Mrs. Benedict insists the girl stay in most all the time and never allows her to look out the windows or talk to girls her age. Marcia and Janet want to unravel this mystery.