Book excerpt: Spirit possession, attachment, poltergeist activity and the negative impact of obsession, infestation and harassment on psychological health, together with the methods of dealing with it, are contemporary issues that demand serious scientific research and academic study. Essential reading for anyone who is presented with the problem of identifying and dealing with negative spirit influence, whether they are a health professional, a service user or a research scientist, this book presents a complementary approach that is built upon the theoretical concepts and experimental methods of Frederic Myers, together with modern research findings in quantum theory and neuro-imaging.