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.