Nat, a veteran of Britain's Secret Intelligence Service, thinks his years as an agent runner are over. But MI6 have other plans. To tackle the growing threat from Moscow Centre, Nat is put in charge of The Haven, a defunct substation of London General with a rag-tag band of spies. His weekly session with the young, introspective, Brexit-hating Ed, offers respite from the new job. But it is Ed, of all unlikely people, who will take Nat down the path of political anger that will ensnare them all.