The movie poster says it all: In Space, No One Can  Hear You Scream  The crew of the space freighter Nostromo encounters a monstrous creature on an unknown planet that begins to stalk and kill everyone on board, one by one. The American Film Institute ranks Alien as the seventh best sci-fi film of all time. It won an Academy Award for best visual effects.  And Sigourney Weaver, a relatively unknown actress, became a world-wide feminist icon playing the heroic character of Ripley.