Extraterrestrials are invading earth, starting with a small town on the Texas/Mexican border. You are part of an elite military unit assigned to protect your team members, the local civilians, while also gathering Intel on how to stop the invasion.
Game play mostly involves switching between a series of first-person perspective hidden cameras, located through the town, in order to hit the extraterrestrials who appear (initially, they appear in human bodies), before they hit you or damage the camera.
Sometimes you are just trying to slow down the invasion, but certain opportunities will arise where you must prevent a civilian or one of your team members from being kidnapped. If you fail at these missions, well it ain't gonna be pretty.
However, if you succeed, you will be able to further the story, which means locating the underground space ship, getting your camera's fixed and obtaining better weapons to incinerate the invaders (who eventually ditch the human bodies).