After US ambassador Jonathan Kraft has given a television interview his aide Ryan Reed is shot dead. The embassy's deputy chief Matt Garcia discovers the married Reed had been having an affair with colleague Terry Lefoe but she has an alibi and terrorism is suspected when Matt receives a parcel bomb which is intercepted. Then Helen Vine, a respected American pathologist who, like Ryan,, had spent time in Africa, is also murdered. Confused psychiatric patient Fergus Weir is released to the care of his sister Ella but disappears and CCTV shows him to have been at Helen's hotel, leading to his arrest and confession. Nikki spends the night with Matt but has a rude awakening.

A private jet crashes into woodland outside London. Among the passengers is a former U.S. Ambassador. Thomas investigates the apparent suicide of a successful businessman, finding unexpected connections to the plane crash.