A group of terrorists take over a company's annual gala at an exclusive high-rise and seize 300 hostages in order to expose the corruption of the hosts. Their just cause is hijacked by an extremist within their own ranks, who is ready to murder everyone in the building to send their anarchic message to the world. 

It falls to an ex-soldier turned window cleaner, played by Daisy Ridley, suspended 90 storeys on the outside of the building, to save those trapped inside, including her younger brother.