DCI Lewis investigate the murder of Bernard Aspen, a soon to be released prisoner who was killed in the prison washroom. He was convicted of child molestation but his case was about to be reviewed and likely stood a fair chance of being exonerated. Although there were as many as eight other prisoners within shouting distance of the murder, no one will admit to having seen or heard anything. DI Richard Mayne volunteers to go into the prison undercover to find the culprit. He focuses on two prisoners, Vic Denton and Donnie Shoreham, as the likely suspects. Lewis isn't aware that he's gone in undercover and his life is clearly in danger when Shoreham learns he's a copper.
—garykmcd