Commander Ryan is suspicious when operator Mike Brady's cover is blown and he escapes from behind the Iron Curtain with three unknown contacts.
When Commander Ryan questions East German translator Magda Rajik her story leaves more questions than answers.
Commander Ryan sends Simpson from the British Embassy, in Berlin, to discover how the Secret Police blew Brady's cover and gets an explosive reply in return. Lt Saunders re-interviews Magda.
The discovery that agent Mike Brady left key information out of his original statement to Commander Ryan becomes damning. Lt Saunders has to decide what his future is.
A tip from the KGB forces Ryan and Sullivan to find an unknown Brit who is going to assassinate a prominent Russian at the launching of a ship in Leningrad.
Soviet dissident, poet Andrei Gourko is rumoured to be in a mental hospital but instead turns up in Britain asking for asylum. The Soviet Union claim he is still in their country.
Berlin Station informs SIS that Charlie Pitman spying in a small village near a nuclear power station. Two days later Pitman is found dead. Major Sullivan goes undercover to find the truth
A civil servant visiting the USA is approached about a classified British project. As it's a top secret project, Ryan has limited number of scientists who are possible suspects.
Soviet agent Ivan Chulkov makes a detour to a East End block of flats before flying to Moscow. Major Sullivan tracks him to the 12th floor but who is his contact?
Ryan and Sullivan are forced to go to East Berlin after they learn that the Unicorn cell cover has been blown. Schroeder had been shot but Ryan needs to find out whether there is a leak in London.
Humanitarian Sir Edward Cockerell plans to use the "Dimbleby Lecture" to expose the British government's plan to allow a Polish scientist to defect only if he works on anthrax fatal to humans.
When cypher clerk Ewan Phillips is found dead there is USSR code book found. Back in 1967, A KGB agent told intelligence there was two moles in M.O.D but after a investigation Alick Stuart cleared them . Ryan is suspicious.
The Melioidosism file has been stolen from Porton Down. Melioidosism is a deadly tocsin with no known antidote. Ryan and Sullivan know it is a chain of couriers, who pass information on but they don't know who has it.
General Merrin, who has recently retired from NATO, has secretly sold his memoirs to a German publisher, receiving a Villa in Nice in return. The publisher is a KGB front in which Ryan needs to discover what damage has been done.