1820s Britain: after the wars with France, when unemployment was high and soldiers could be paid off, when the government was desperately afraid of social unrest, any crime was drastically punished and thousands were hung. But one could petition the King and an investigation might ensue...

The man in the dark cell in Newgate Prison was due to hang in a week. He had been found guilty of murdering the aristocrat whose portrait he was painting. He claimed to be innocent - but then the hangman had never hung a guilty man, he said. But even in 1820, the Home Secretary could occasionally use his powers to grant mercy if his investigator found cause and Rider Sandman, once of the First Foot Guards, is given the job.