Set in modern-day London, a group of radical activists seize control of an energy company’s annual event and take 300 people hostage in an attempt to expose the corruption of the host company. Their just cause is hijacked by an extremist from among their own members, who is willing to kill everyone in the building to send his anarchic message to the world. A former soldier, played by Daisy Ridley, plays a window cleaner hanging 50 stories above the building’s exterior, and must rescue those trapped inside, including her younger brother.