Tracing the role of the informer through history, from the "fig babblers" of Ancient Greece to Britain's supergrasses of the 1970s, this book also explores the behaviour of the police and private detectives in infiltrating criminal enterprise. It examines the fine line between undercover agent and agent provocateur, in locations ranging from Ireland to America. The author's other books include "Gangland", "Nipper", "Bent Coppers" and "Mad Frank"