After distinguishing himself by courageously neutralising a terrorist threat, troubled war veteran Police Sergeant David Budd of the Metropolitan Police's Royalty and Specialist Protection Branch (RaSP) is assigned as a principal protection officer to the home secretary, the Rt Hon Julia Montague MP.

Another terrorist attack raises the UK threat level to severe. Home secretary Julia Montague holds secret meetings with the director general of the security service, freezing out the police and her own minister of state for counter terrorism.

As the capital shudders in the wake of two terrorist attacks, specialist protection officer PS David Budd is more under pressure than ever to keep the home secretary Julia Montague safe. The threat to her life does nothing to curb Julia's political ambitions, as her counterterrorism bill takes another step towards being made law, provoking political rivalries.

Struggling to come to terms with the traumatic events of the last 24 hours, the home secretary's bodyguard David Budd himself falls under suspicion.

David investigates Julia's political manoeuvring and finds his fears about a conspiracy at the heart of government could be justified. However, doubts are raised about his psychological health as allegations about his professional conduct come to light.

Principal Protection Officer David Budd has made a major breakthrough in the investigation into the attack on the home secretary, but his enquiries have put him in mortal danger. With the clock ticking and no-one left who believes him, David attempts to prove his innocence. But the evidence against him begins to stack up.