SeasonsevenofBritishspythriller"MI-5"openswithAdamCarter(RupertPenry-Jones)valiantlybattlingtomoveacarbombawayfromadenselypackedmemorialservice.MeanwhileHarrysecuresthereleaseofLucasNorth(RichardArmitage),aMI-5officerimprisonedinRussiaforeightyears.It'snotlong,however,beforeRosbeginstosuspectLucas'loyalties.TherestoftheseasondealswithatopsecretColdWar-eraoperationnamedSugarhorse.