Set in present-day London, a group of radical activists take over an energy company’s annual gala, kidnapping 300 guests in order to expose the hosts’ corruption. Their righteous cause is hijacked by an extremist within their own ranks, who is ready to kill everyone in the building to send his anarchic message to the world. It falls to a former soldier turned window cleaner, played by Daisey Ridley, to hang herself 50 stories from the outside of the building to save those trapped inside, including her younger brother.