Someone Is Always Watching By Kelley Armstrong

Blythe and her friends—Gabrielle, and brother and sister Tucker and Tanya—have always been a tight friend group, attending a local high school and falling in and out of love with each other. But an act of violence has caused a rift between Blythe and Tucker . . . and unexpected bursts of aggression and disturbing nightmares have started to become more frequent in their lives.

The strange happenings culminate in a shocking event at school: Gabrielle is found covered in blood in front of their deceased principal, with no memory of what happened.

Cracks in their friendship, as well as in their own memories, start appearing, threatening to expose long-forgotten secrets which could change the group’s lives forever. How can Blythe and her friends trust each other when they can’t even trust their own memories?