Aliens are perfect creatures, the ultimate killing machines whose physical superiority combines with their thirst for destruction. Officer Ellen Ripley and a spaceship crew have got acquainted with them already, and only Ripley managed to survive. After many years drifting in space her escape vessel is found by rescuers and Ripley learns that planet LV-426 is colonized and she has to return there to restore the connection with the colonists. Who will survive: monsters, that can only kill, or people, whose only weapon is ability to think?