Set in present-day London, a group of radical activists take over an energy company’s annual party and take 300 hostages in an attempt to expose their hosts’ corruption. Their righteous cause is hijacked by an extremist within their ranks, ready to kill everyone in the building to send his anarchic message to the world. A former soldier turned window cleaner, played by Daisey Ridley, must hang 50 stories from the outside of the building to rescue those trapped inside, including her younger brother.