Experiments in biological warfare have destroyed all but a few remnants of the human race. Alone in a lab, eight students work feverishly to create a vaccine before they are forced outside in search for food. It is then that the surviving scientists discover creatures mutated by the plague. Now they prepare to do battle against their worst fear: The Terror Within.

In a world gone mad, the last human colony struggles to survive underground, beneath a land of nightmarish mutants who seek to destroy them. But when the mutant breaks inside humanity's final stronghold, the battle for survival pits the human colonists against their deadly invaders miles below the earth's surface.