The work begins with an arresting line: “It was somewhere between my 34th and 39th year when I began to go crazy.” In the 1980s, the author was living with her husband and three children in a yellow-brick house outside Philadelphia. She says that she began to hear conflicting voices in her mind, which she initially interpreted as ordinary thought processes. However, she also felt her love for her children was weakening, and she couldn’t understand why. Later, her spouse revealed to her that he’d been having an affair with another woman. During the messy divorce that followed, Barrett’s relationships with her kids deteriorated as well, although she exceled in her career as a schoolteacher. Soon, she realized that the voices she was hearing seemed to have personalities of their own; one was called “Rosie,” which claimed to be the voice of the author’s twin sister. When she was 43, Barrett found a therapist to help her with her condition, now known as dissociative identity disorder. There was likely some trauma at the root of it, said the therapist, but Barrett couldn’t remember what it was. The book recounts her efforts to discover it and how she tried to get some semblance of her previous life back. Barrett’s prose style is precise and rich, and she excels at communicating her complex emotional states, keeping the reader grounded even when she describes the experience of switching between personalities: “Over time, parts of me began to talk when I was in the therapy room….A yawn was indicative of a switch as I moved from myself to an alter….Eventually, out of the nothingness a voice would emerge.” Overall, it’s a compelling exploration of a misunderstood disorder and of the various ways it can complicate a person’s life. The book also effectively serves as a meditation on how small incidents can result in a significant crisis over time and on the significant amount of work that’s required to live life with a troubled mind.