The year is 2122. The USCSS Nostromo spacecraft is a space tug that was 39 lightyears away returning to Earth when it receives an unknown transmission from a nearby moon called Acheron (LV-426).
The ship’s computer MU/TH/UR 6000 familiarly known as Mother then follows the secret orders of the Weyland-Yutani Corporation, which prioritizes obtaining Aliens and any other alien life form found on expeditions, treating all employees as disposable resources.
In the first phase of this adventure, you will be the synthetic employee and science officer Ash, who was awakened by the computer and tasked with waking up the rest of the crew, decoding the message and going to the planet to respond to this supposed SOS from an unknown alien civilization.
In the second phase, you will be warrant officer Ellen Ripley, responsible for descending with part of the crew to the planet to look for the origin of the call. After you find a destroyed alien ship with its crew dead but containing several strange creatures (known as facehuggers) and dangerous alien eggs, you must rescue the crew and return safely to the Nostromo.
In the third and final phase, still as Ellen Ripley, you decide (against Weyland Corp instructions) to avoid the extremely dangerous Alien (Xenomorph XX121) that was brought aboard from Acheron being taken to Earth, even if it means blowing up the Nostromo. For that you have to escape both the Alien and the facehuggers spread throughout the ship.