They tried to kill him - now he wants revenge.

Someone is killing old spies. Retired and forgotten, these relics from the Cold War are being removed—quietly and brutally.

And when “Section D” MI5 agent Tom Marlowe, on medical leave after a botched mission learns his old mentor is one of the murdered ex-agents, he starts an investigation that threatens to cost him his career, his freedom… and even his life.

Uncovering a conspiracy linked to a late-eighties operation called RUBICON, one involving long-forgotten Russian sleeper agents, now operating in the highest echelons of Westminster, Marlowe is thrown down a rabbit hole that forces him off the grid and on the run, hunted by his own people.

Out in the cold, with his air supply cut off, burned from working with any allied agency and with only disavowed spies to rely on, Marlowe must try to clear his name and expose this threat, before the US President is assassinated during his next London visit, and a new World War begins...