Someone Is Always Watching by Kelley Armstrong

The experiment began with the best of intentions: help a young child who is responsible for a traumatic death. Maybe their entire family perished in a fire they set. Maybe they shoved their sibling off a balcony during an argument. If the child is too deeply traumatized - and stigmatized - to ever lead a normal life, wouldn't it be better if they just . . . forgot? It was a three-pronged approach: erase their memories, insert new ones, and return them to their parents or place them with a new family. Blythe and her friends Tucker, Tanya, and Gabrielle, are now teenagers, attending a local high school, falling in and out of love with each other. But then a shocking event happens at school: Gabrielle is found covered in blood in front of their deceased principal, with no memory of what happened. It's becoming apparent that their pasts weren't erased - they were just walled up, and now those walls are crumbling.