The crew of the commercial towing vessel Nostromo finds themselves being awoken from hyper-sleep prior to their arrival at Earth. The ship's computer has diverted them a mysterious planet, where it picked up an signal of unknown origin. After landing on the planet, the ship's captain, Dallas, it's navigator, Lambert, and the second-in-command Kane go to investigate, while the rest of the crew - Warrant Officer Ripley, Science Officer Ash, and the engineers Brett and Parker work on repairs and monitor Dallas's team's progress...