What's it about? Sigourney Weaver stars as Ellen Ripley alongside Tom Skeritt, John Hurt, Ian Holm and Harry Dean Stanton as members of the crew on board the commercial spacecraft the Nostromo, returning to earth. After answering a distress signal they find their ship invaded by a deadly alien creature which hunts the crew down one by one.What makes it groundbreaking? Ridley Scott's first masterpiece is also the first truly successful marriage of horror and science fiction. The production design alone - especially the incredible creature design from H. R. Giger - has been imitated countless times since but never bettered, while the bare-bones approach to atmosphere and tension and the lean, mean screenplay still allow room for an undertone of sexual commentary. Weaver's scene-stealing strong central performance established her as one of the best actresses of her generation.