This chapter introduces the main themes of the book. Disruption has hit the audit market where the Big Four currently dominate the main body of audits for all major enterprises. The failure of a number of companies, most notably Carillion in 2018, has led to widespread criticism of the external auditors. An explanation of the current situation in the audit market is provided, particularly the lack of real competition, and explains how following the new audit rotation and other regulations, there are too few firms to provide reasonable choice. The chapter explains why the failure of Carillion is such a pivotal event and explores the decline of audit quality in the Big Four. It also introduces the authors team and sets out the research methodology behind the series.