Inside the US Embassy, the celebrations for a newly appointed US Ambassador to London are shattered when a call, threatening to blow a British plane out of the sky if anyone leaves, triggers an immediate embassy lockdown, trapping guests and staff inside. 

And that's when the murders begin, landing Hana Li, as a British cop, in a political and jurisdictional nightmare. Compelled to join forces with the Head of Embassy Security, Clay Brody, played by Martin Compston, a former colleague who once screwed her over, Hana has to see her way past her distrust of him and focus on the investigation. Because this time it's personal. The plane that will be blown up is a government jet and Director General Madeline Delaney is onboard.

With a killer wreaking havoc inside the Embassy and evading them at every turn, Hana and Brody must discover who is behind the treacherous plot before time runs out for the hostages within the Embassy and the passengers on board Delaney's plane.

After attending a medical conference in Beijing and coming frighteningly close to dying in a car crash, Dr. Matthew Nolan arrives home and is immediately arrested at London's Heathrow Airport. Exhausted and confused, Nolan is accused of the murder of a woman who was in the car he crashed. Despite his protests that he was driving alone, Nolan is set to return to China to face charges. 

DC Hana Li is the no-nonsense London officer charged with accompanying Nolan back to Beijing. Her resentment for this assignment, and of Nolan himself, is immediate. However, in flight, when a first death occurs, DC Li begins to suspect foul play. Further deaths confirm that Nolan is in danger, and after a call from MI5, Hana finds herself embroiled in an escalating conspiracy.