Nat, a 47 year-old veteran of Britain’s Secret Intelligence Service, believes his years as an agent runner are over. He is back in London with his wife, the long-suffering Prue. But with the growing threat from Moscow Centre, the office has one more job for him. Nat is to take over The Haven, a defunct substation of London General with a rag-tag band of spies. The only bright light on the team is young Florence, who has her eye on Russia Department and a Ukrainian oligarch with a finger in the Russia pie.