The unfilmed action sequence would have shown Parker observing the Alien as it enters the airlock, only for it to be startled when an alarm goes off. The Alien is wounded by an automatically closing door, causing acid to spill. The ship's pressurization is threatened and the Alien manages to escape into an air vent. The scene then returns to Lambert on the bridge.
Alien 5 being a prequel confirmed-: http://www.totalfilm.com/news/alien-5... It's actually a prequel movie that will explain the origins of the space jockey spaceship.
Plot: The story begins when the crew of the commercial transport ship Nostromo receive a transmission which might be of nonhuman origin.
They land on the deserted moon Acheron LV-426 and find a derelict spaceship with a dead alien and many large eggs.
Directed by Ridley Scott © 20th Century Fox
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This article covers all the known deleted scenes from the 1979 film Alien. Some of these...