Set in modern-day London, a group of radical activists take over an energy company’s annual gala and take 300 hostages to expose the corruption of their bosses. Their just cause is hijacked by an extremist within their ranks who wants to kill everyone in the building to send his anarchist message to the world. The task falls to a former soldier turned window washer, played by Ridley, who is suspended 50 stories above the ground by a building to rescue the people trapped inside, including her younger brother.