A cargo ship (Nostromo) is ordered by the company to investigate a strange crash landed ship. After their shuttle lands a three man away team onto the ship. They discover a face hugger alien who attaches itself to the second officer's (Kane) face. Back on the ship the doctor (Bishop) cannot get the alien off. Later they find a way to detatch it. During a meal Kane's chest explodes and releases a baby alien who was growing inside of him. The remaining crew make differant plans to kill the Alien. Every time a member of the crew is killed including the captain. Third officer Ripley (played by Sigorne Weaver) takes command of the ship. She finds out on the ship computer that the company wants them to deliver the alien to earth where it can be researched by the company. She makes plans to abandon the ship but Bishop attacks her. When the other crew members arrive they mamage to cut off Bishop's head and discover him to be an android who is loyal to company. Ripley makes preparations to escape onboard a single man escape ship, then blow up the Nostromo to kill the alien. The other members of the crew are killed by the alien and Ripley escapes with the ship cat. The Nostromo self-destructs but Ripley finds the alien sleeping onboard the escape ship. She opens an air lock and the alien is sucked into space. The movie ends with her sending out a call for help to any nearby ship.
Space travel is extremely slow so crew members must spend time in hyper sleep for years possibly.
The Nostromo is a massive ship but it only requires the a crew of seven.
There is a brief scene where Ripley is seen in her underwear. This is when she has to put on space suit to protect her from the ship when the air and the alien are sucked into space.