Paul Ready as Rob Macdonald, a special adviser to the Home Secretary

Richard Madden as PS David Budd, a war veteran and Specialist Protection Officer Keeley Hawes as Julia Montague, the Home Secretary

Vincent Franklin as Mike Travis, the Minister of State for Counter-Terrorism Pippa Haywood as CSI Lorraine Craddock

The aftermath of a major incident leaves the country in shock and Budd's world in ruins. He is under intense scrutiny and must navigate a web of lies and deceit to find the truth. The investigation into the attack reveals deep-seated corruption and hidden agendas.

Police Sergeant David Budd, a war veteran, is off-duty when he thwarts a suicide bombing on a train. His actions lead to him being promoted to the protection detail of the Home Secretary, Julia Montague. Montague is an ambitious politician who is pushing for new surveillance powers. Budd is secretly struggling with PTSD and is disillusioned with the government's involvement in the wars he fought in.