As one of the UK's leading commentators, David Wilson shows how some serial killers stay in the headlines whilst others rapidly become invisible - or "unseen". Yet Mary Ann Cotton is not just the first but perhaps the UK's most prolific female serial killer, with more victims than Myra Hindley, Rosemary West, Beverly Allit or male predators such as Jack the Ripper and Dennis Nilsen. But her own north east of England (and criminologists) apart, she remained largely forgotten until the release of the ITV series 'Dark Angel', which was inspired by this book. This despite poisoning to death up to 21 victims in Britain's 'arsenic century'. Exploding myths that every serial killer is a 'monster', the author draws attention to Cotton's charms, allure, capability, skill and ambition - drawing parallels or contrasting the methods and lifestyles of other serial killers from Victorian to modern times. He also shows how events cannot be separated from their social context - here the industrial revolution, growing mobility, women's emancipation and greater assertiveness. And concerning the reticence of 'human nature', like Dr Harold Shipman, Cotton was allowed to go on killing despite reasons to suspect her. The book contains other resonances to aid understanding of how serial murderers can go undiscovered despite such things as coincidence, gossip, whispers or motives that become more obvious with the benefit of hindsight. It is also a detective story in which the persistence of a single individual saw Cotton tried and executed, events analysed first-hand from the archives and location visits as the author fills the gaps in a remarkable story.By a leading expert on serial killers. Meticulously researched and highly readable. Fresh interpretations mean this book is destined to be the definitive title on Mary Ann Cotton.Review: 'An enthralling read.David Wilson does not write generic "true crime", but history of the highest order': Judith Flanders, best-selling author, journalist and historian.