No one knows how many people have been wrongfully convicted. But for every one of them, there's someone else who has escaped justice. The dream that, somehow, that guilty person will be found has got to haunt the jail cells of the innocent but rarely is that dream realised.

When an innocent police officer in Warwick, Rhode Island was sent to prison for murder, he had no idea that his salvation would lie not in DNA or the courts but in the conscience of a man he had never met.