The Twenty-Four-Hour Lipstick Mystery by Bonnie Pryor, 1989.
Cassie Adams, who is eleven years old, has never been happy with her looks, and now that her friends are starting to shave their legs and get interested in boys, she feels plainer than ever. One day, she sees an ad for Mrs. DuPrey’s School of Beauty and Charm and thinks that it might help her improve her appearance and develop confidence. The only problem is that she doesn’t have the money for it, and her parents won’t give her any. She decides that she needs to look for odd jobs in the neighborhood to help raise the money that she needs.
By coincidence, old Mr. Murdock’s granddaughter has recently moved into the old family house, which is huge and reputed to be haunted. In spite of the creepiness of the old place, Cassie finds a job there, helping Miss Murdock with cleaning and unpacking. Miss Murdock’s father made his money in cosmetics, and Miss Murdock employs a secretary named Victoria Presser, who used to be a model. Cassie admires Vicky for her beauty and elegance and looks forward to picking up some beauty tips from her. She also makes friends with Jason, a new boy in town, who also works for Miss Murdock, helping the gardener fix up the grounds. However, it isn’t long before Cassie, Jason, and Cassie’s younger brother, Danny, begin noticing that there is something odd about the old Murdock house.
Danny is the first to notice that there is an octagonal window in the wall of the house, but none of the rooms has a window in that shape. Sometimes, lights can be seen through this window at night. Also, Cassie finds what looks like lab equipment among Miss Murdock’s boxes. Is Miss Murdock involved in something illegal? Does it have something to do with the burglaries that have been occurring around town? Why is the grumpy old gardener sneaking around? Just what is in that hidden room?
This is a good mystery for tween and early teen girls, who can identify with Cassie’s worries about being beautiful and popular. The moral of the story is that appearances are deceiving, and in the end, Cassie reconsiders what beauty really is and develops more confidence by appreciating the good qualities she already has and developing new interests. While some of the other girls try to show how grown-up they are by looking grown-up, Cassie really grows up by taking responsibility for her life and the direction she wants it to go, making decisions about what she wants and who her real friends are.