One night in 1990, a stranger cut the screen out of Nancy McCabe's bedroom window while she slept and shone a flashlight into her eyes as she woke. A few weeks later, her father came down with temporary amnesia. Although unrelated, these events became linked in her mind, sweeping out from under her the fundamentals many of us take for granted: safety, freedom, the stability of memory, and a general oblivion to mortality. After the Flashlight Man...