Defence of the Realm

A car carrying two men is chased by the police on a foggy night. They reach a dead-end road and are forced to stop; one man escapes over a barbed-wire fence while the other is captured. The tense opening sets the mood of danger and suspicion that threads through the story.

A London newspaper reports Dennis Markham seen leaving a woman's home on the same night as a German attaché's visit. The article questions his loyalty and sparks a debate about whether the story should be printed. Editors weigh public interest against potential political fallout.

Vernon Bayliss is called to a private meeting with Markham and explains a connection to a German agent, a link Markham does not know about. The disclosure casts Markham in a more suspicious light and deepens the political intrigue.

Nick Mullen interviews Nina Beckman, Markham's secretary, and then speaks to Markham's wife while posing as a policeman. The interviews uncover tensions around Markham and begin threading together the personal and political narratives.

The story written by Mullen breaks as the 'Markham Affair' on television and in the newspapers, spreading quickly across media outlets. Public interest spikes as more details emerge and the case dominates the headlines.

Markham is hounded by the media and pressured to resign from public life. The relentless coverage leaves little room for doubt about his political future. The public's fascination with the scandal grows as the plot thickens.

Mullen learns that Bayliss dies from a supposed heart attack on the same night his flat is ransacked by someone who leaves no obvious valuables behind. The coincidence suggests a broader conspiracy at work and raises the stakes for the investigation.

Mullen breaks into Bayliss's desk and uncovers press-cuttings and a tape that insinuate a different motive behind the attack on Markham. The newly found material hints at hidden forces manipulating the political crisis.

Mullen visits the young man who was caught at the start of the film and tells him that his accomplice is dead. This meeting redirects the investigation toward a deeper, more elusive mastermind behind the events.

Mullen returns to the site where the film began and discovers a high-security USAF base near Brandon. He realizes the UK–US nuclear weapon capability is entangled with the Markham affair, suggesting motives beyond personal scandal.

With Nina Beckman's help, Mullen continues the investigation despite break-ins at his flat and other attempts to thwart him. The collaboration keeps the pressure on the hidden agendas at play.

Mullen goes to publish the story, but his editor informs him that the Official Secrets Act blocks it. The newspaper owner, Kingsbrook, has intervened to suppress the piece, raising questions about who controls the truth.

Mullen discovers that the 'KGB agent' was actually a British agent, and he confronts Anthony Clegg in a gentleman's club. Clegg is grabbed by two men and taken to an office for questioning by senior officials, showing the reach of those who wish to keep the truth buried.

A bomb explodes at Nina's flat as she steps inside, likely killing them both. Earlier, Nina had posted incriminating evidence to Germany, and the near-nuclear-disaster story spreads across European press, ensuring the fallout is global.