When an old friend of DI Declan Walsh is murdered and an old enemy restarts their vendetta against him, he's placed in charge of solving the case alongside his fellow detectives in the Last Chance Saloon Crime Unit; DCI Alexander Monroe, DS Anjli Kapoor, DC Billy Fitzwarren, Doctor Rosanna Marcos and her assistant DC Joanne Davey, realizing in the process that somewhere in Whitehall a new narrative is being written for the murder; one where the dead body is leaked to the press as an Extremist Terrorist, and Declan is being set up to be revealed as not only their terrorist handler in the UK, but also the prime suspect for the murder.

Now working against the clock and trying to find a way to find the real killer before being publicly "outed" as a terrorist, in the process forced to abandon his family and home and escape from his own team, Armed Response units and Special Branch, Declan learns that the hunt is now being led by another old foe with a score to settle-and one that will happily kill Declan if it means capturing him.

Off the grid and running scared, Declan's forced to not only use his police skills but also his military background to survive, gaining help from unexpected sources and going deep undercover while fighting a vicious rival with unlimited resources.