The player takes the role of corporal Dwayne Hicks, taking part in the mission to rescue settlers from the Hadley's Hope colony on LV-426.
Gameplay and layouts are influenced by the first Alien vs Predator game from 1999, as well as the classic Alien Trilogy from 1996.
- E1M1: Main Colony Complex
- E1M2: Med. Lab and Operations
- E1M3: Atmosphere Processor
- E1M4: USS Sulaco
Several demo versions were released before the final version. The first demo was released in early 2007 as a beta. It contained three maps and some material taken from Justin Fisher's Aliens TC. It was mostly known only on the Spanish forums at arcades3d.com.
A pair of ZDoom demos were released around 2008, though only one reached the main public on some forums.
The main and most well know demo had three levels, two of them based on LV-426 colony (later taken and modified for the final release) and another one only released in the demo based on an orbital station in space.
The first areas of the map E1M2: Med. Lab and Operations are a remake of Justin Fisher's "Aliens TC" map E2M3: Med-Labs and Operations. This map appeared in the second ACM demo as a straight remake with the same goal (seal off the med lab) and layout. It was later cut, edited, and joined with parts of another map.