The Undeclared War

While Danny deals with the aftermath of the Russian cyberattack, Saara discovers a mole at GCHQ.

Vadim finds himself working for a Chinese cyber enterprise; the mole hunt begins at GCHQ.

When Barbara's ex reappears in her life, she is forced to make a decision she'll forever regret.

Chinese malware attacking British government departments forces Roz and Danny to work together.

Charlie's search reaches Barbara; Danny discovers a clue that turns his life upside down.

Danny finds out the truth as both the malware attack and the mole hunt come to a head.