On what should have been a trip back to Earth, the Nostromo, a mining freighter, is automatically re-routed to a desolate planet after receiving an SOS coming from it. After the crew is awakened, they investigate the source of the SOS, and discover a derelict alien ship on the planet. One of the crew members is put into a coma by an alien creature while investigating the ship. But the alien parasite dies and the crew think all is well. But the small ordeal was only a prelude for greater things to come.
