InseasonsixoftheBritishespionagethriller,theteamarepushedtotheirlimits,astherelationshipbetweenBritishandAmericansecuritydeterioratesandloyaltieschange.AdamandRosfightagainstanemergingterroristthreat,andadeadlyvirusthatcoulddecimateLondon.Thisseasonbreaksawayfromthecase-by-caseepisodicformat,withonedominantstorylinetyingalltheactiontogether