After a space merchant vessel perceives an unknown transmission as a distress call, its landing on the source moon finds one of the crew attacked by a mysterious lifeform, and they soon realize that its life cycle has merely begun. In the distant future, the crew of the commercial spaceship Nostromo are on their way home when they pick up a distress call from a distant moon. The crew are under obligation to investigate and the spaceship descends on the moon afterwards. After a rough landing, three crew members leave the spaceship to explore the area on the moon. At the same time as they discover a hive colony of some unknown creature, the ship's computer deciphers the message to be a warning, not a distress call. When one of the eggs is disturbed, the crew realizes that they are not alone on the spaceship and they must deal with the consequences.