Mike Harding was due to be discharged after twenty two years service in the British Army. Several of those years were spent at Hereford with a Special Forces regiment. It was because of the skills he acquired while at Hereford that the Ministry of Defence was reluctant to lose him so instead of being discharged, he was offered an opportunity to join MI13, a covert department within the Ministry of Defence headed by Major Challenor, a former British Army officer.

Two Russian agents from a secret assassination unit, disembarked from a French trawler when the boat put in for repair at a small port on Scotland's west coast. They had joined the trawler at Calais, while masquerading as experienced trawlermen. They had orders to make their way from the port to Faslane where they were to distribute Ricin at any place fin Faslane frequented by submariners. A Syrian woman and her son was with them. After being taken from the infamous 'jungle' refugee camp at Calais where the woman accepted an offer made by the two men she could not refuse, It was agreed that provided she assisted the two men to complete a simple task, she and her son would be given free passage to the UK,

In London a bicycle courier attempted to deliver a suspicious package to the offices of MI3 at Victoria Street. Major Challenor became suspicious and called in the bomb squad. The Officers from the squad sent the package to Porton Down for analysis. When the technicians opened the package they found it contained Ricin. It could only mean one thing. The purpose of the attempted delivery was to destroy MI13.

The courier's failure to deliver the package resulted in his controller, a sleeper agent resident in Brighton, receiving orders from Moscow to send him to join the two Russians already at Faslane. Meanwhile, at HM Naval Base Clyde, the numbers of submariners falling ill was increasing rapidly. Medical checks revealed the men had been poisoned with Ricin. The base commander contacted Major Challenor with a request for urgent assistance. Having agreed to the commander's request, Challenor sent Mike Harding and two MI13 colleagues to Scotland. It didn't take long for Harding and his colleagues to apprehend two of the three Russians known to be spreading the Ricin but the third Russian, the one believed to be the leader of the group, escaped. He was still at large when a Glaswegian taxi driver was murdered in his cab. A CCTV image showed the killer to be the third Russian. The search for the missing Russian intensified. The Prime Minister stressed the man must be caught before he immobilised still more submariners serving in the nuclear submarine squadron. If that were to happen it would put the entire squadron at risk of not being able to put to sea, causing irreparable damage to national security, putting the entire UK at risk of an attack by an enemy. Harding's orders were clear. He and his colleagues must find and apprehend the Russian at all costs. The use of extreme prejudice is authorised and they are to terminate him if necessary.