Informers have been active during many periods of unrest in Ireland but, until Tudor times, they had never been an organized phenomenon until the twentieth century. The decision (or refusal) to inform is dangerous—thus the motives of the informers are compelling, as is their ability to deceive themselves.

Drawing on firsthand and newspaper accounts of the Easter Rising and other events, this book provides a history of the gradual development of informing in Ireland. Each informer's story details their life and secrets and the outcome of their actions. All of them have shared two experiences: the accusation of informing, whether true or false, and betrayal, whether committed or endured.