Three years into their jobs as response officers, Constables Grace Ellis, Tommy Foster, and Annie Conlon are operating at their limit, facing a new threat on the streets that the police can barely control. Meanwhile the murder trial of Gerry Cliff exposes a dangerous and long-buried secret that leads to chaos both inside the police, and across the criminal underworld. As they grapple with big decisions about their future, Grace, Tommy and Annie must find the courage to face the greatest threat they have ever encountered: the truth.

Two years into their jobs as response officers Grace, Annie and Tommy are accustomed to life under the blue lights. But their work will take them into a sinister world hidden behind the veneer of middle-class life, the world of the accountants and lawyers who facilitate organised crime. The old political and criminal order has gone and a new global gang rule Belfast, bringing danger closer to home for our officers than ever before.

Grace, Annie and Tommy are growing up fast as police officers, but nothing can prepare them for the turmoil they face every day. It's a year since the fall of the McIntyre crime gang and the vacuum has been filled by rival gangs, all competing for dominance. Constable Shane Bradley is drafted in to help, but his motivations are unclear. Tommy is dangerously seduced by the world of intelligence policing, while Grace struggles to deal with her son's absence, and growing feelings for fellow officer Stevie. As a young loyalist threatens to take over the city, the officers face a major gangland feud – culminating in a violent and devastating confrontation.