The Watcher, written by Ross Armstrong, is a psychological suspense novel that delves into the dark world of voyeurism and surveillance. The story follows Lily Gullick, a woman who becomes obsessed with her new neighbor, Jean, and begins spying on her through her apartment window. As Lily's voyeuristic behavior escalates, she discovers that Jean is not as innocent as she seems. The Watcher is a chilling exploration of the boundaries between privacy and surveillance, and the consequences of crossing those lines.