The Fourth Protocol

As the fragile peace forged by the 1968 East-West agreement began to take hold, a delicate balance of power was maintained through strict protocols, including the Fourth Protocol, which prohibited unconventional methods for delivering nuclear weapons. However, amidst this backdrop of international cooperation, a clandestine operation was underway in Britain.

MI5 officer John Preston (character A) embarked on a clandestine mission to infiltrate the residence of government official George Berenson, uncovering top-secret NATO files that were not supposed to be there. His unauthorized tactics led to embarrassment for Acting Director Brian Harcourt-Smith, and as punishment, Preston was demoted to handle "Airports and Ports" – a far cry from his previous responsibilities.

Meanwhile, KGB officer Major Valeri Petrofsky (character A) received orders from General Govorshin, the head of the KGB, to breach the Fourth Protocol by assembling and detonating an atomic device in a false-flag operation. The plan aimed to create the illusion of an American nuclear accident at a nearby military base, ultimately straining British-US relations and bolstering the anti-nuclear movement ahead of a crucial election that favored the Soviet Union.

In Glasgow, tragedy struck when a Soviet sailor was hit by a truck while attempting to evade port authorities. Amidst the chaos, Preston discovered a disk of polonium among the deceased's belongings – an item with no purpose other than as a component in a bomb detonator. Believing he had stumbled upon something significant, Preston reported his findings to Harcourt-Smith, only to be promptly suspended due to his perceived attempts to fabricate an incident and regain favor within MI5.

However, Preston enjoyed the trust of Sir Bernard Hemmings, the gravely ill Director of MI5, as well as high-ranking official Sir Nigel Irvine. With their support, Preston continued his investigation, ultimately tracking down Winkler, a notorious Czech KGB agent, from the airport. As tensions mounted and alliances were tested, Preston found himself at the forefront of a perilous game of cat and mouse, racing against time to prevent catastrophe and uncover the truth behind the sinister plot unfolding before him.

As Petrofsky's relationship with Irina Vassilievna, a cunning KGB agent posing as his wife, deepens, he finds himself unwittingly entangled in a web of deception. Under her guidance, they assemble the bomb components, and she sets it to detonate on a two-hour delay - or so Petrofsky believes. In reality, Vassilievna has reset the timer to zero, setting in motion a catastrophic chain of events. After their intimate encounter, she attempts to warn him about the double-cross, but her efforts are cut short as Petrofsky silences her permanently.

Meanwhile, Preston's pursuit of Petrofsky takes him on a wild goose chase across Ipswich, finally tracking him down near RAF Baywaters. It becomes clear that Petrofsky's target is the airbase itself, and Preston locates his house mere yards away from the perimeter. As Petrofsky prepares to activate the bomb, he hesitates for just a moment, checking the timer before realizing too late that he has been betrayed. The SAS team storms the property, and in the ensuing struggle, Preston manages to subdue and disable Petrofsky. However, his relief is short-lived as one of the operatives callously takes out Petrofsky, citing orders from above.

At Hemmings' funeral, Preston's suspicions are confirmed when he catches Irvine huddled with General Karpov. The revelation sparks a sense of disillusionment within Preston, who had been following Winkler, a known KGB operative, and had grown increasingly uneasy about Petrofsky's demise at the hands of his supposed captors. It becomes clear that Irvine and Karpov are engaged in a cynical game of power play, using discrediting Govorshin as leverage to further their own careers. Preston's disgust with their tactics is palpable, but he ultimately decides against exposing them, choosing instead to rejoin his young son and distance himself from the treachery that has unfolded before him.