The Home Secretary's Principal Protection Officer David Budd (Richard Madden) struggles to come to terms with the fallout from the devastating events of the last 24 hours. The police retake control of the investigation into the attacks from the suddenly weakened Security Service and David is questioned by counter terrorism detectives DCI Deepak Sharma (Ash Tandon) and DS Louise Rayburn (Nina Toussaint-White). Pushed to breaking point, David is helped back on his feet by his estranged wife, Vicky (Sophie Rundle), and is determined to play an active role in the investigation, starting with those closest to Julia in government. At first Rayburn wants to keep David out of the enquiry, until he delivers a breakthrough.