When commercial towing vehicle Nostromo, heading back to Earth, intercepts an S-O-S signal from a nearby planet, the crew are under obligation to investigate. After a bad landing on the planet, some crew members leave the ship to explore the area. 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 call for help. When one of the eggs is disturbed, the crew do not know the danger they are in until it is too late.
