In modern-day London, a group of radical activists take over an energy company’s annual gala and take 300 hostages to expose the hosts’ corruption. Their righteous cause is hijacked by an extremist in their ranks who is willing to murder everyone in the building to send his anarchic message to the world. A former soldier turned window cleaner, played by Daisey Ridley, has dangled from the outside of the 50-story building to save those trapped inside, including her younger brother.