Watcher In the Dark by Beverly Hastings (Paperback) Berkley Publishing 1986,
Book cover shows mild wear, inside clean, no personalization.
Erin is a babysitter for a little girl named Abby. Erin gets crank phone calls while babysitting. Abby's father has to go out of town for a few days and leaves the child in Erin's care at his home. This makes no sense. Erin lives not very far away with her parents, why wouldn't the father have her take Abby to her home for a few days instead of leaving them in the empty house?
Anyway, Erin keeps getting the hang-up calls. One day Abby's long-lost mother, Annette calls ranting about coming to get her baby. Erin hasn't seen Annette in nearly two years. Erin starts getting scared all alone in the house with Abby. Eventually she starts suspecting that someone has been in the house when they were out. One night Dan, Abby's half-brother comes into the house unannounced.
Anyway, Annette apparently ends up following Erin around. Erin gets even more frightened and decides to take Abby to her house, but her parents had to fly to Canada on an emergency. Suddenly the phone calls from Annette start. How the heck does Annette know Erin's home phone # when she can barely recall what day and month it is? Far-fetched.
Erin gets even more frightened and decides to flee with Abby to Abby's family's cabin, right, because Annette wouldn't know about the cabin that she spent a lot of time in. She'd never think to look there Erin.
Anyway, lots of other details not worth mentioning happen. I liked the book, but it was not all I had hoped