Section D are forced to welcome an FSB Officer onto the Grid to help track down Aibek, a rogue nationalist from the ex-Soviet state of Azakstan. Aibek is in the UK to find the last known sample of the nerve agent 'Paroxocybin'. The chase is on, but will the team find a way to stop the nerve agent falling into the wrong hands without ruining Anglo-Russian relations? Meanwhile, Lucas's personal life takes a passionate turn.
Elenco: Peter Firth , Nicola Walker , Matthew Macfadyen , Richard Armitage , Keeley Hawes , Hermione Norris , David Oyelowo , Max Brown , Lara Pulver , William Hope , Anna Chancellor , Sophia Myles , Natasha Little , Richard Harrington , Shauna Macdonald , Gemma Jones , Alex Lanipekun .