As the murder of a diplomatic courier leads DS Hana Li to London's US Embassy, MI5's Madeline Delaney receives a call about a bomb on the jet she is travelling on.

As Hana and Brody search for the killer, the embassy is put into lockdown but Fox remains one step ahead of them - meanwhile, a bomb is found on Delaney's jet.

When a second embassy guest is murdered, it's discovered that both victims were part of a panel that blamed the crash of the D-300 on Russia.

Hana finds a clue which changes everything, Delaney and Peterson try to defuse the bomb onboard the jet, and Banks and Jess uncover vital evidence.

Hana and Brody set a trap to catch Fox, Jess enlists surprising medical help to save Ruth's life, and the true architect of the conspiracy is finally revealed.