Enemy Territory

Enemy Territory is a science fiction first person shooter video game.

Plot
A government research outpost on Mars is taken over by a rebel group of mercenaries known as the Occupants. Chance Kincaid, a rookie soldier at the United Space Corps, is chosen for delicate mission of launching an assault on the base and taking it back. However, only after he arrives is his team killed and he finds himself alone on the base with the Occupant forces as well as the mutated experiments, which have escaped captivity at the base.