Ash was the Science Officer transferred aboard the Nostromo prior to it's destruction in 2122.
The events onboard the NostromoEdit
Ash was a Hyperdyne Systems model 120-A/2 that was created for Weyland-Yutani in the early part of the 22nd century. Ash was later switched in to the Nostromo's roster by the company to oversee a specific retrieval mission, thereby replacing another science officer from that roster two days before the Nostromo departed from Thedus.
It was at Ash's insistence that the crew investigated the mysterious signal emanating from LV-426. Ripley became suspicious of him when he broke quarantine protocol by allowing Kane, Dallas, and Lambert to re-enter the Nostromo while the Alien facehugger was attached to Kane.
Ash and Captain Dallas attempted to remove the creature from Kane's face but the creature tightened it's grip around his neck. Ash later tried with a lase scalpel to remove one of the "digits" of the creature and it bleed acid that ate through several floors in the ship. He later called Dallas down to the infirmary to inform him that the creature released itself from Kane's face. Dallas, along with Ripley and Ash looked for the creature around the infirmary and the creature landed on Ripley dead. Ash later dissected the creature and was interrupted by Ripley and was growing annoyed by her questions.
Ash later notified Captain Dallas that Kane's condition changed and that he was now conscious. After Kane was visited by the crew, Dallas told the crew that he would get the last meal before going back to hypersleep. Ash joined the crew for the last meal and was present when Kane went into convulsions and helped restrain him. As Ash and the others restrained Kane, a creature ripped out of his chest killing him. As Parker was going to kill the creature, Ash talked Parker out of killing it and before the crew could catch it it escaped into the ship.
After the crew came up with a plan to catch the creature, Ash developed a motion tracker to find it easier. The crew split up in to two teams with Ash being with Dallas and Lambert. Ash later heard that the creature grew to at least the size of a man and that it attacked Brett and took him into the vents.
Ash was later paired up with Ripley when Dallas volunteered to go into the ducts to flush the creature out and blow it out the airlock. As Dallas made his way through the ducts, a signal came up on the tracker and Lambert yelled at Dallas to get out of there as the signal was moving towards him. Unfortunately, the creature got Dallas in the airducts and all Parker found was his incinerator.
After the Alien killed Dallas, Ripley discovered through the ship's computer "MOTHER" that Ash has been given special orders by the Weyland-Yutani Corporation to ensure the return of the Alien to the company's laboratories, even at the expense of the crew. When confronted by Ripley, Ash attacked her. He was hit in the head by Parker, and the force almost completely severed his head. It was at this point that Ash was revealed to be an android. After suggesting that the crew would not survive the Alien's attacks and giving them his sympathies, Ash was destroyed by Parker using a flamethrower.
Due to his betrayal of the crew, Ripley harbored a deep distrust and hatred for androids that would stay with her decades later. She would later take the hatred she had for Ash out on another synthetic: Bishop. By 2179 inhibitors were in place to prevent synthetics from "malfunctioning" and harming or letting harm come to a human. Ash's picture was displayed during a debriefing about the Nostromo on Gateway Station on the fate of the ship and her crew. The events on the Nostromo also left a distrust towards the Weyland-Yutani Company for putting the lives of others aside to study and harness the potential the xenomorphs had. This also shaped Ripley's decison making skills during her future encounters with the creatures.