Events pivot around Charles Thoroughgood (Charlie Cox), a wet-behind-the-ears MI6 agent whose university friendship with Russian diplomat Viktor Koslov sees him fast-tracked into the middle of a urgent campaign to undermine Operation Legacy, a Soviet plot to destroy British infrastructure. But what will he find in this dark hinterland? Clearly peril and betrayal, but also shocking information about his own family and – via unhappily married espionage widow Anna (Romola Garai) – an insight into the emotional hazards of a life lived in such shark-infested waters.
Like most of Milne’s work it’s earnest to a fault, but also psychologically credible thanks to Cox and Garai’s expressive and committed performances. It also looks great: the permanent dusk of blackout 1974 is exploited to maximum effect.