Complex sentence: The film takes place right after the events of "Aliens" (1986), an escape pod from the Colonial Marine spaceship "Sulaco" crash-lands on a prison-run refinery planet, killing everyone aboard except Lieutenant Ellen Ripley (Sigourney Weaver).
Split into simpler sentences: The film takes place right after the events of "Aliens" (1986). An escape pod from the Colonial Marine spaceship "Sulaco" crash-lands on a prison-run refinery planet, killing everyone aboard except Lieutenant Ellen Ripley (Sigourney Weaver).