In January of 1999, an otherwise nonviolent man under great stress at work brutally murdered his wife in their backyard. He then went back to bed, awakening only when police entered his home. He claimed to have no memory of the event because, while his body was awake at the time, his mind was not. He had been sleepwalking. In this book, the author, a sleep scientist, brings together decades of research into the bizarre sleep disorders known as parasomnias to propose a new theory of how the human mind works consistently throughout waking and sleeping hours. Thanks to increasingly sophisticated EEG and brain imaging technologies, we now know that our minds do not simply "turn off" during sleep. Rather, they continue to be active, and research has indicated that one of the primary purposes of sleep is to aid in regulating emotions and processing experiences that occur during preceding waking hours. As such, when sleep is neurologically or genetically impaired or just too short, the processes that good sleep facilitates, those that usually have a positive effect on our mood and performance, can short circuit, with negative results that occasionally reach tragic proportions. Examining the interactions between conscious and unconscious forms of thinking as they proceed throughout the cycles of sleeping, dreaming, and waking, the author demystifies the inner workings of the human mind that trigger sleep problems, how researchers are working to control them, and how they can apply what they learn to further our understanding of the brain. Along the way, she provides an account of the history of sleep research and the birth of sleep medicine that will initiate readers into this field of inquiry and the far reaching implications it will have on the future of neuroscience. This work offers a look at a relatively new area of study that will be of interest to those with and without sleep problems, as well as anyone captivated by the mysteries of the brain, and what sleep continues to teach us about the waking mind.