The situation worsened when the survivors discovered that Ash was a synthetic assigned by the Company to preserve the creature and bring it back to Earth. The creature matured into an adult and began killing the crew members one by one. Within 20 hours, Kane died when the creature within him burst violently out of his chest during the crew's pre-hypersleep meal and fled to the farthest reaches of the ship. Kane was taken back to the Nostromo for medical treatment and the ship departed. Executive Officer Kane was impregnated by a parasitic life form discovered within an ancient derelict space craft. The crew members were woken prematurely from hypersleep and landed on the planetoid to investigate. While returning to Earth from Thedus, the Nostromo was diverted to the Zeta II Reticuli system when the ship's mainframe intercepted a distress beacon originating from an uncharted planetoid (later named LV-426).

There is also a ginger tomcat named Jones (often called 'Jonesy' by the crew). Ripley's failure to complete the process resulted in the ship's destruction. Cancelling the self-destruct sequence was a complicated procedure. There was an option to override the process prior to the last 5 minutes of the countdown. The ship also had a self-destruct system, which shut off the reactor cooling units, causing the engines to overheat and detonate precisely 10 minutes after initiation. The ship had numerous industrial areas, a central eating area, a hypersleep chamber, a kitchen, a cockpit, and an infirmary. The mainframe piloted the ship while the crew were in hypersleep and monitored their activities. The ship was equipped with a MU-TH-UR 182 model 2.1 terabyte AI mainframe (called 'Mother' by the crew), available to command officers through a special interface room. It was connected to the ore refinery platform via an umbilical detachment system. The ship itself weighed more than 60,000 metric (66,138 US) tons, included three decks, four holds, stores, and engines and a shuttle named Narcissus.

The ore refinery it towed was 1,927 metres (6,322 feet) long, 1,257 metres (4,124 feet) wide, and 1,131 metres (3,712 feet) high, processing raw material on the long trip to Earth. Valued at $42 million in adjusted dollars, the Nostromo was 334 metres (1095 feet) in length, 215 metres (705 feet) wide and 98 metres (320 feet) height. It hauled a mile-long ore refinery that, on its final voyage, processed 20 million tons of raw ore. The Nostromo, an M-Class Lockmart CM 88B Bison starfreighter, was property of the Weyland-Yutani Corporation.

Nostromo novel