Harry kidnaps and interrogates his CIA counterpart (William Hope) in hopes of confirming CIA complicity in the assassination attempt on the Russian emissary. Later, he and Ruth infiltrate the U.S. Embassy in an attempt to steal a notebook computer that contains sensitive information.
The team works to stop a suicide-bomb plot by two released prisoners, one of whom is an MI-5 asset. Elsewhere, Harry comes across additional evidence indicating CIA involvement in the assassination attempt on the Russian official; an attempt is made on Elena's life.
An anarchist may be building dirty bombs; the intelligence theft is linked to an assassination attempt on the Russian ambassador. In other events, the home inspector asks Ruth to become his security adviser.
The series' 10th and final season opens with a former colleague of Harry's murdered. In other events, Harry is suspicious of an old KGB rival, who's in London to coordinate a strategic partnership between the U.K. and Russia.