When commercial towing vehicle Nostromo, heading back to Earth, intercepts an SoS 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.

Originally to be directed by Walter Hill, but he pulled out and gave the job to Ridley Scott.

Dallas:
[looks at a pen being dissolved by alien's body fluid] I haven't seen anything like that except, uh, molecular acid.


Brett:
It must be using it for blood.


Parker:
It's got a wonderful defense mechanism. You don't dare kill it.

Incorrectly regarded as goofs: In the opening scene, we see the reflection of a computer screen on the helmet with a cup on the right. When we see the helmet again, it is showing a different screen, so the cup is not present.

Written by Howard Hanson