MI5 officer Winnie Monks has never forgotten the death of a young agent on her team at the hands of a former Russian army major turned gangster. Now, 10 years later, she learns that the major is travelling to a villa on the popular Spanish holiday destination Costa del Sol, and she asks permission to send in a surveillance unit. They find an empty property near the major's. It's a perfect base for Winnie's darker, less official plans. But it turns out the villa isn't deserted.

Northern Ireland, spring 1981. Hunger strikes, riots, power cuts, a homophobic serial killer with a penchant for opera, and a young woman’s suicide that may yet turn out to be murder: on the surface, the events are unconnected, but then things—and people—aren’t always what they seem. Detective Sergeant Duffy is the man tasked with trying to get to the bottom of it all. It’s no easy job—especially when it turns out that one of the victims was involved in the IRA but was last seen discussing business with someone from the loyalist Ulster Volunteer Force.

Officially, the Cold War is over, and the hand of friendship has been exchanged in public. In private, though, the intelligence war continues. A British trawler strays into Russian waters. On its return, the captain has a package for British Intelligence. For the next four years, a high-ranking Russian naval officer provides MI6 with priceless information. But suddenly he goes quiet. Clearly under suspicion, the decision is made to get him out. But his controllers in London know nothing about him.

In a Croatian village near Vukovar, no one who survived will ever forget the night they waited for the weapons they needed to make a last-ditch fight against the advancing Serbs. The promised delivery never came, and the village was overrun. Eighteen years later, a body is unearthed from a field, and with it the identity of the arms dealer who betrayed them. Now the villagers can plot their revenge. In leafy England, arms dealer Harvey Gillott regards himself as a man of his word. There is only one blemish on his record, and that was long ago.

Two years ago, a hostile Prime Minister launched the Monochrome inquiry, investigating "historical over-reaching" by the British Secret Service “to investigate historical over-reaching.” Monochrome’s mission was to ferret out any hint of misconduct by any MI5 officer—and allowed Griselda Fleet and Malcolm Kyle, the two civil servants seconded to the project, unfettered access to any and all confidential information in the Service archives in order to do so. But MI5’s formidable First Desk did not become Britain’s top spy by accident, and she has successfully thwarted the inquiry at every turn.