Geneva, 2012. When a Russian intelligence officer approaches MI5 with vital information about the imminent cyber-sabotage of an Anglo-American Defence programme, he refuses to talk to anyone but Liz Carlyle. But who is he, and what is his connection to the British agent? At a tracking station in Nevada, US Navy officers watch in horror as one of their unmanned drones plummets out of the sky. Is this a Russian plot to disable the West’s defences? Or is the threat coming from elsewhere?

Liz Carlyle is a smart, impassioned MI5 intelligence officer. When one of her agents reports suspicious meetings taking place at an Islamic bookshop, she trusts her instinct that a terrorist cell is at work. But she's surprised when her boss suddenly takes her off the case and shocked to hear why: he has received a tip-off that a mole, a "secret asset", has been planted in one of the branches of British Intelligence.

MI5 officer Liz Carlyle is posted to Northern Ireland. From the moment she lands in Belfast, danger follows. She soon discovers that the peace process in the province is precarious. Then a source reports strange goings-on at a house on the Irish Sea owned by the Fraternity, an organisation Liz suspects of being a front for renegade former IRA men. Its head is Seamus Piggott, an Irish-American with a gun-running past.

When pirates attack a cargo ship off the Somalian coast and one of them is found to be a British-born Pakistani, MI5 Intelligence Officer Liz Carlyle is brought in to establish how and why a young British Muslim could go missing from his family in Birmingham and end up on board a pirate skiff in the Indian Ocean, armed with a Kalashnikov. After an undercover operative connected to the case turns up dead in a shipping office in Athens it looks like piracy may be the least of the Service’s problems...

In 2012, in a Middle Eastern souk, CIA agent Miles Brookhaven was attacked. He was infiltrating rebel groups in the area and no one was certain if his cover had been blown or if the act was just an arbitrary attack. Now, Liz Carlyle and her Counter Terrorism unit in MI5 have been charged with the task of watching the international under-the-counter arms trade and British Intelligence forces have become increasingly concerned that extremist Al-Qaeda jihadis are building their power base ready to launch another attack.