In the year 2117, a race of aliens known as the Arelians have enslaved the human population of Earth using their henchmen, the savage Zorn. They insert implants into infants' brains at birth, to be able to track them. As soon as someone turns 30, the aliens take the person away and nothing is known about their subsequent fate. The main character, Jorel, after losing both his parents to the alien invaders, decides to flee south to Mexico to join the rebel forces and fight the alien invaders. Thanks to his strong psionic resistance, his brain rejected the implant and he brings new hope to the desperate human race looking for a leader.
Later, the true nature of the Zorn and Arelians is revealed. The Arelians, bored of the collective mind of the alien race, enslaved the humans for entertainment. The Zorn, in return for helping the Arelians, were to be allowed to eat any human above the age of 30.
Unlike the X-COM games, there is no base building, resource management or research. During combat, the player controls a squad of characters and must accomplish various goals. Characters have a certain amount of action points, which are renewed at the beginning of every turn. Each action, from turning to walking to shooting consumes action points. Therefore they are only allowed to perform a certain amount of actions per turn.
The player may also pick up and use weapons from dead aliens. As ammunition is limited, it is sometimes useful to loot an enemy's corpse in order to keep fighting.
There are many weapons available such as knives, pistols, assault rifles, machine guns, sniper rifles and grenades. As characters specialize in different areas, it is important to adopt a strategy that will fully utilize the strength of each of the weapons used. It is also possible for a character to act as a medic, using a medikit to heal comrades.
Every time characters damage an enemy, heal an ally, or use psonics, they gain experience points. Once they have enough, they gain a level which raises their attributes such as strength, constitution, and intelligence at random. They also gain one skill point which the player can assign to a skill of their choosing, such as heavy weapons, hand-to-hand combat, medicine, or stealth. Thus, as the game progresses, each character becomes stronger and they may specialize in a type of weapon or skill above all others.