In modern-day London, a group of radical activists storms an energy company’s annual gala and takes 300 hostages to expose the organizers’ corruption. Their righteous cause is hijacked by extremists within their own ranks, ready to kill everyone in the building to send their anarchic message to the world. It falls to a former soldier turned window washer, played by Daisey Ridley, to hang herself from the 50th floor of the building to save those trapped inside, including her younger brother.