The Undeclared War

A newly arrived intern at GCHQ breaks ranks to investigate a major malware attack on the UK.

Saara and Kathy decrypt an anonymous invitation to a conference attended by Russian intelligence.

Vadim takes a covert job to assert his independence. His allegiances are soon put to the test.

Amid civil unrest, Saara is devastated to learn the identity of a mole inside GCHQ.