Roy J. Snell 
Third Warning / A Mystery Story for Girls [EPUB ebook] 

Florence and Marian continue their mystery solving adventures in another story! Mr. Snell is a versatile writer who knows how to write stories that will please boys and girls. He has traveled widely, visited many out-of-the-way corners of the earth, and being a keen observer has found material for many thrilling stories. His stories are full of adventure and mystery, yet in the weaving of the story there are little threads upon which are hung lessons in loyalty, honesty, patriotism and right living. Mr. Snell has created a wide audience among the younger readers of America. Boy or girl, you are sure to find a Snell book to your liking. His works cover a wide and interesting scope. (Excerpt from Wikipedia)