A leading team of analysts buried in the heart of GCHQ, secretly works to ward off a series of cyber-attacks on the UK in the run-up to a general election. When a routine stress test of internet infrastructure goes awry, 21-year-old GCHQ intern Saara Parvin suddenly finds herself operating on the invisible frontier of high-stakes cyber warfare. In a thrilling cat-and-mouse game, Saara and the team at GCHQ must try to stay one step ahead and anticipate their opponents' every hidden move.

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.