A young intern's first day at GCHQ coincides with a major cyberattack on the UK; to win her superiors' trust, she breaks ranks to analyze the malware code without permission and uncovers a greater threat missed by others.

Saara befriends John, a veteran GCHQ staffer, and seeks help from Gabriel in decrypting a message in the virus; Danny signs off on Saara attending a cyber conference with US agent Kathy, aware that Russian intelligence will also be there.

Vadim takes a covert job to assert his independence and starts an affair with a co-worker; the FSB notices his talents and coerces him to work on the cyber weapon project, putting his allegiances to the test.

Marina moves to London for a new opportunity; Danny is unconvinced by information Saara shares from an anonymous source; Saara's hand is forced when Kathy informs her that GCHQ is about to reveal the names of the FSB coders.

Sredi državljanskih nemirov je Saara pretresena, ko izve za identiteto krta v GCHQ.

As the true extent of Russia's interference with the UK becomes clearer, Saara and Vadim realize that only an act of ingenuity and extraordinary bravery could uncover the hidden level in the malware code and prevent a war.