The fourth of these was meant to prohibit non-conventional deliveries of nuclear weapons, i.e. by means other than being dropped from aircraft or carried on ballistic missiles.

On New Year's Eve 1986, professional thief James Rawlings breaks into the apartment of a senior civil servant and inadvertently discovers stolen top secret documents.

In Moscow, British defector Kim Philby drafts a memorandum for the Soviet General Secretary stating that, should the Labour Party win the next general election in the United Kingdom (scheduled for sometime in the subsequent eighteen months), the "hard left" of the party will oust the moderate populist Neil Kinnock in favour of a radical new leader who will adopt a true Marxist-Leninist manifesto, including the expulsion of all American forces from the United Kingdom and the country's withdrawal from (and repudiation of) NATO.

In conjunction with a GRU general, an academic named Krilov, and a chess grandmaster and experienced strategist, they devise "Plan Aurora" to secure a Labour victory by exploiting the party's support for unilateral disarmament.

John Preston, an ex–Parachute Regiment soldier-turned-MI5 officer, who was exploring hard-left infiltration of the Labour Party, is assigned to investigate the stolen documents and discovers they were leaked by George Berenson, a passionate anti-communist and staunch supporter of apartheid South Africa.

Berenson passed on the documents to Jan Marais, who he believed was a South African diplomat, but who was in fact a Soviet false flag operative.

As part of Plan Aurora, Soviet agent Valeri Petrofsky arrives under deep cover in the United Kingdom and establishes a base using a house in Ipswich.

Irvine, however, suspects that a major intelligence operation is underway, and has Preston work unofficially for him to search for other Soviet couriers (his absence from the office being justified by the coincidental order to take leave).

A month into the investigation, a bumbling Czechoslovakian operative, originally believed to be an Austrian, under the name 'Franz Winkler' arrives at Heathrow with a forged visa in his passport and is shadowed to a house in Chesterfield.

By sending Winkler, Karpov thwarted a British publicity victory as Irvine understood the implication that Petrofsky must not be caught alive or exposed in the media.