Film is forever.
You know the story already. Ripley's suicide in the previous film complicates things, but not much, and before the first reel is out a cloned Ripley is back on her feet and the alien fetus she was harboring in her chest is maturing nicely. A gang of shady characters then arrives bearing a mysterious cargo, and the stage seems set for a cozy, predictable bloodbath. Except this time there's something odd about Ripley, like the way she can tear open steel bulkheads with her bare hands, and the way her blood sizzles when it hits the floor. Sigourney Weaver makes the most of this struggle, giving a riveting performance that blows everyone else off the map, including the creatures themselves, whose scariness, after three previous movies' worth of exposure, has largely evaporated.