Alien Trilogy is a first-person shooter that combines all three Alien movies into one quest broken into three chapters. Each chapter focuses on a different aspect of its respective movie, but does not follow the order in which they were released.
You begin on LV426 -- the setting of the sequel, Aliens. The game then flows into the prison colony of Alien 3 and finally comes to a close aboard the derelict spacecraft from the original Alien. Regardless of their order, each quest requires the completion of missions loosely based on those of the movies. They range from going from point A to point B to destroying the Queen's nest. Each one intertwines with the overall storyline, which is told via cinema sequences rendered and inspired by the movies.
Also lifted from the movies are the way the three sections are presented in atmosphere, mood, and level design. Most corridors are dark and ominous and attempt to embrace the player with a feeling of suspense and fear. All of the creatures seen in the movies have been included, such as the face-hugger and regular aliens. If it's not killed fast enough, the former will jump up on your face/screen and begin sucking your life away.