S1, E1: London: 1972. When a defecting KGB officer, Arkady Malinov, reveals Operation Glass, a devastating Soviet plot that could change the course of the cold war, Daddy, the head of MI5, assembles a secret team to investigate. As the Soviets awaken a list of sleeper agents all over Britain, Daddy’s team must move swiftly to gain information about the plot. But when Joe Lambe, Daddy’s prized agent, becomes obsessed with the reappearance of a dangerous nemesis, a Soviet agent codenamed ‘Odin’, he risks letting his personal vendetta jeopardise the operation.