A prison officer has clearly been caught off guard and is found shot dead on a council estate in North London. Was he a good guy targeted by an inmate – or was he a bad boy who crossed the wrong villain?

DS Ronnie Brooks and DS Jamie Bamber are called on to investigate the murder of Prison Officer Charlie Tyner. Initial evidence suggests Charlie was a clean-living, upstanding, exemplary Officer. But after digging a little deeper Brooks and Bamber uncover a dirty side to Charlie which shows he was as bent as a £9 note and using his position of trust to get up to all sorts. All this means that there are plenty of people who wanted Charlie dead and Brooks and Bamber know just where to look for them: in prison. So, as the most likely suspects are already behind bars with cast-iron alibis, the police have to look outside to find who put a bullet in Charlie – and why.

Crown Prosecuting Services Director George Castle wants Charlie’s killer brought to justice. But his team of James Steel and Alesha Phillips are a bit less gung-ho on this case: they think Charlie’s abuse of his position should be considered when his killer is charged. They also want to use the case to catch another crook – one who has evaded justice for too long.