The worst criminals are sentenced to live their lives on an island turned maximum security prison where there are no guards, no rules, and the only escape is death. On the island, various factions battle for control of the island.
John Carpenter's vision of the near future was considered innovative. Problem is, it was already passé
Eight years previously, in 1973, Terminal Island did the exact same idea. Not nearly as well, but hey - being first count for something, too! TI is an exploitation film when being an exploitation film was cool. As such, it has certain shortcomings inherent to the genre, such as street talking tough black guy, the psychotic white chauvinist pig, and the heroic woman, overcoming oppression with sagacity and perseverance.
Marta finally gets to play the part of an action hero. She fights and blows things up and knows how to create gunpowder from nature. Very cool.
Of course, while tossing a Molotov cocktail, she ends up riddled with automatic weapon fire, but no script is perfect.