The relationship between the CIA and MI-5 are put to the test when things go wrong in Afghanistan.
A trio of Chinese agents arrive in London and the team must find out why.
Beth goes undercover for the first time for MI-5.
Beth and Dimitri go undercover as Home Office representatives, in order to protect the American president who is in London for top-secret peace talks.
An FSB Officer is welcomed onto the Grid to help track down a rogue nationalist from Azakstan.