The shocking new psychological thriller from the bestselling author of A Man Downstairs and An Unthinkable Thing: a twisty, unsettling, and masterfully plotted game of magnetic push-and-pull between two women whose secrets threaten to collide.

When Mia was a young woman, she read a magazine article about a murderous teenage girl with a rare and disturbing psychiatric delusion. Fascinated by the details, she sought out the doctor who’d treated the girl, and eventually married him. Twenty years later, Mia’s curiosity is piqued once again when her husband announces that his famous case study will be republished—and that he will be reconnecting with his former patient.

Lainey has never felt that her feet are fully on the ground—not since she was released from a psychiatric institution at the age of twenty-one. When her former doctor reaches out, she decides to tell him the truth about what happened all those years ago. Perhaps she can finally lighten the darkness that has defined her entire existence.

With mirroring software, Mia pores over every recorded therapy session with Lainey, almost as though she’s watching a true crime drama unfold. On the opposite side, Lainey becomes intensely interested in her doctor’s family. How far will she go to insert herself into his seemingly perfect life?