The London branch of DedSec, led by Sabine Brandt and her newly crafted AI, Bagley, detect armed intruders planting explosives in the Houses of Parliament. DedSec operative Dalton Wolfe goes to defuse the bombs and discovers the intruders are members of a rogue hacker group called "Zero Day". Although Dalton manages to prevent Parliament's destruction, he is gunned down by drones commanded by Zero Day's leader, who detonates additional explosives around London and orders an attack on DedSec's main hideout, forcing Sabine to shut down Bagley and go into hiding. In the wake of the bombings, the British government contract Albion with restoring order to London and hunting down DedSec, who are held responsible for the chaos, effectively causing social and political unrest.

Months later, Albion enforces the law without political oversight, transforming London into a surveillance state with the aid of its ctOS network and SIRS, a conglomerate of Britain's intelligence agencies. As a result, citizens have their personal liberties severely restricted and their lives constantly monitored, while those who question Albion's methods are either convicted or deported to Continental Europe. Organised crime is also on the rise, despite Albion's presence. Although most DedSec members have been arrested or killed by Albion, Sabine resurfaces when she finds a new recruit through ctOS, who is sent to reactivate the group's safehouse and Bagley. DedSec slowly rebuild their strength as they find more recruits who, under Sabine's co-ordination and with Bagley's help, liberate London's boroughs by encouraging citizens to rise up in defiance of their oppressors.