This book seeks to bring understanding of both complexity and temporality into criminology. It outlines why these are important in criminological models of causation and explanation and explores them by drawing on theories and approaches in political science, comparative history, social theory and systems analyses. It discusses what is meant by complexity and introduces historical institutionalism (which is rarely used in criminology) to criminological audiences; it introduces what is known as ‘why-because’ analyses to the social sciences. This style of thinking is used to explore the causes of major transportation accidents (such as aeroplane or ferry disasters) and involves the integration of structural, organisational and agentic inputs in accounting for such disasters. Chapters on realistic evaluation, theories of structuration and agency, and research design and research methods are included with an example project based on the author's recent studies of Thatcherism which shows how these theories can be applied to empirical data. This book speaks to those interested in criminology, sociology, political science, research methods and the wider social sciences.