You've got your "Saw" and "Hostel," your "Nightmare on Elm Street" and "Friday the 13th" — horror films in which there are monsters who are programmed to torture, dismember and kill. You've got your "Rosemary's Baby" and "Exorcist," your "Omen" and "Poltergeist" — in which evil spirits and boogeymen threaten you with their paranormal or spiritual devilry.

But "The Ruins" star Jena Malone insists the devil and the devil's henchmen don't hold a candle to the scariest villain of all: you.

"What I really liked about 'The Ruins,' what I felt set it apart, is there's no evil character. There's no bad guy, no guy with a gun that's shooting up and you gotta watch out behind the shadows," she said of the horror film, out Friday, which pits a group of American tourists against a somewhat-undefined villainy amid ancient Mayan ruins. "The creepy nature is human nature. That's what makes it so strange and weird — it's a part of us all."

Like his earlier film "A Simple Plan" — which took the thriller genre and turned it inside-out by focusing more on, well, the interior motivations and doubts of the main characters — author Scott Smith's "The Ruins" is less about exterior threats (though, to be sure, it does have them) than it is about "what happens when you're actually fighting for your basic urge to live," Malone posited.

"It strips you down so you no longer have your cute little catechisms: how you like to paint your nails, who you are with your best friends, the jokes you acquire. You're stripped down to your basic need of having water and the will to survive," Malone said of the film's true evil. "What animal comes out of you in the midst of such deprivation?"

For Scott, what came out is "the best horror novel of the new century," according to Stephen King. For the characters at the heart of "The Ruins," however, including Malone and former "X-Men" star Shawn Ashmore, what comes out is what goes in — the whispers and gossip and poisons the characters bring with them to an archeological dig, where they are soon trapped with no hope of rescue.

Boxed in, they start to turn on each other, and in one of the film's most graphic scenes, one character even turns on himself to perform a graphic surgery in the middle of the desert.

It's scenes like this that serve as "a reminder of what we are," Malone contended.

"There is something technical about it, something inside of us, the chemicals that are living and dying and different circumstances that bring out these beasts inside of us. It's the way you put on lotion in the morning and the toxic exchange of your chemical dependencies. Things that make people turn in the strangest ways," she said. "It's so much more interesting when people are afflicting themselves rather than being afflicted — the history of violence within us all."

Check out everything we've got on "The Ruins."

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