Student Saara wins a coveted internship at GCHQ, but when a significant part of the UK's internet goes down, she quickly finds herself operating on the frontier of high-stakes cyber warfare.
Saara finds a suspicious line of encrypted text within the virus's code and unravels a dubious invitation. Is she getting closer to the truth or falling into a trap?
Saara's classmate Vadim returns to St Petersburg. He reluctantly takes a covert job and soon becomes the victim of his own success as his allegiances are put to the test, leading him to a risky stunt.
With Danny unconvinced by Saara's exchange with a whistleblower, she's in a difficult position, but a revelation from Kathy forces Saara's hand. Meanwhile, Marina takes up a new opportunity in London.
Signs of irregularity in the UK general election result prompt political unrest, and the nation's relationship with its allies is threatened. Saara makes a devastating discovery.
As the true extent of Russia's interference with the UK becomes clear, Saara and her former classmate join forces. Can they uncover the hidden code and prevent a war?
Danny is under huge pressure dealing with the fallout from the Russian cyber-attack when a bold new threat emerges. Saara discovers that there’s a mole in GCHQ. And Vadim is missing and in danger...
Vadim realises that he must try to escape captivity in Shenzhen. Back at GCHQ, Danny and Roz clash over China. And has Charlie unearthed the mole?
When Barbara's charming ex-boyfriend, Nicky Chan, re-appears in her life, she must make an impossible decision.
While Danny becomes increasingly concerned about Barbara’s erratic behaviour, malware causes havoc across British government departments, forcing Danny and Roz to work together.
Barbara comes under Charlie’s scrutiny as tragedy strikes GCHQ. Danny, Saara and Roz attempt to help Vadim escape. And Danny makes an earth-shattering discovery.
Danny puts everything on the line in order to right some wrongs. Meanwhile, Roz and the team must race against the clock to find out what the malware is searching for.
