Episode 1

London, 1972. A war has unfolded unlike anything anyone has ever known. A complex and invisible war fought not by armies but individuals. The secret services on both sides of the Iron Curtain would exploit any weakness to further their aims.

When a defecting KGB officer reveals details of a devastating Soviet plot, the charismatic head of MI5 must assemble a secret committee to help protect Britain. As the Soviets awaken sleeper agents to carry out the plot, the new team are faced with an unidentified, invisible threat. The first agent has been blackmailed into working for the KGB. As MI5 scramble to identify his role in Operation Glass, Joe Lambe becomes obsessed with the reappearance of his nemesis, the Soviet agent codenamed 'Odin'.