In 1988 IRA terrorist Sean O'Callaghan walked into a Tunbridge Wells police station and gave himself up. Two years later, in a Belfast courtroom, he pleaded guilty to all charges of which he was accused and received a sentence of 539 years. Since being a teenager he had been an active member of the IRA and had risen to be the head of their Southern Command. He was responsible for two murders and many terrorist attacks. He was a linchpin of the organization.

But in 1996, he was released from prison by royal prerogative. For fourteen years he had been the most highly placed informer within the IRA and had fed the Irish Garda with countless pieces of invaluable information. He prevented the assassination of the Prince and Princess of Wales at a London theatre, he sabotaged operations, explained strategy and caused the arrests of many IRA members. He has done more than any individual to unlock the code of silence that governs the IRA's members, and has in effect made it possible to fight the war against the terrorists. Under constant threat of IRA revenge, he now works ceaselessly for peace in Ireland. As he says, 'I hope to use the time available to me now to tell the truth about the IRA. I will go on doing that for as long as it takes.

The Informer is Sean O'Callaghan's story. It is the story of a courageous life lived under the constant threat of discovery and its fatal consequences. It is the story of a very modern hero, who is not without sin but who has done and is continuing to do everything in his power, and at whatever personal cost, to atone for the past.