This introduction presents an overview of the key concepts discussed in the subsequent chapters of this book. The book outlines the time scale and the geographical location of the research and goes on to debate the concept of 'deviance' and 'sexual deviance'. It considers personal testimony as a historical source, and discusses key moments in the history of sexuality and mental health nursing. The book discusses that with the outbreak of World War II, there appeared to be a relaxing of attitudes towards homosexuality. It examines and interprets the testimonies of the 'subversive nurses'. The book explores the inception of 'nurse therapists' and discusses their role in administering aversion therapy. It then deliberates the implications of the changes and examines how nurses began to view medical treatments for sexual deviation as inappropriate as ideas of deviance shifted.