Shannon believed her husband's affair was the ultimate betrayal. She was wrong.

Shannon has the kind of perfect life others envy. After an idyllic getaway with her husband, Scott, and their teenagers, she reluctantly returns home, thinking work demands are the only stresses that await her-but then she reads the messages of deception on Scott's phone.

Devastated but determined not to crumble like her mother before her, Shannon keeps up appearances for her children. But behind her polished suburban routine, she quietly steps into the shadows, discovering the dangerous thrill of being desired by someone new. Reclaiming herself feels exhilarating.

Until her phone lights up with a message from an unknown number: I know what you are. Soon, the texts are constant, accompanied by strange, subtle disturbances in her home, some even while she sleeps. Someone is watching, judging, and tracking her every move-and they know far more than her schedule. They know her double life, her hidden guilt, and her deepest vulnerabilities.