When radical eco-activists take over a skyscraper gala, seizing 300 hostages to expose a corrupt energy company, their cause is hijacked by a violent extremist ready to kill everyone. The only person who can stop the massacre is Joey Locke (Daisy Ridley), an ex-soldier who works as a window cleaner and happens to be suspended 50 stories up on the outside of the building. She must infiltrate the tower to save the hostages, including her younger brother.