The film takes place in modern London. A group of radical activists hijacks an energy company’s annual gala and takes 300 hostages to expose the owners’ corruption. Their righteous cause is hijacked by an extremist from among them, who is ready to kill everyone in the building in order to bring his anarchic message to the world. A former soldier turned window cleaner (played by Daisy Ridley) has to hang 50 stories outside the building to save those trapped inside, including her younger brother.