Set in 2024, immediately after the end of season one, the team in the Malware Department at GCHQ come to terms with a massive Russian cyber-attack. But just as the British finally gain the upper hand, Danny and his team realise that Russia were not the real architects of the attack. They have a new adversary who is set to attack. And not only that, but the team realise that they have a mole in GCHQ.