As the cuddle 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 hugger, 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 cuddled, 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.

The true nature of the conspiracy is revealed as Hana and Brody overcome their personal demons and work with Delaney to deliver justice.