Set in present-day London, a group of radical activists take over an energy company's annual banquet and take 300 hostages to expose the hosts' corruption. Their just cause is hijacked by an extremist in their ranks who is prepared to kill everyone in the building to send his message of anarchy to the world. It follows an ex-soldier turned window cleaner, played by Ridley, suspended 50 stories outside the building to rescue those trapped inside, including her younger brother.