Scott Smith hadn't even finished writing The Ruins - and Stephen King had not yet hailed it as "the best horror novel of the new century" - when Hollywood started clamoring for the rights to turn it into a film.
Smith was only two-thirds done with the book when Ben Stiller's production company, Red Hour Films, snapped up the screen rights based on an outline of the plot. "They told me they wanted me to write the screenplay, too," Smith says. "So while I was writing the last third of the book, I already knew I'd be adapting it for the movies."
This helps explain why The Ruins - the harrowing tale of a group of vacationers stranded on a hill in the Mexican jungle where some wild, evil things grow - is such a cinematic read. An instant bestseller when it was published in the summer of 2006, the novel is filled with passages that practically scream to be put on film, such as a nerve-racking descent into a pitch-dark crevice in the earth where something ancient - and hungry - lies waiting.
It's ironic, then, that the film adaptation of The Ruins opening Friday differs so much from the book. Although the basic narrative remains the same, several surprises await fans of the novel, many of them effective, while a few - like the new ending - more open to debate.
What hasn't changed is the Big Bad in The Ruins, which joins the ranks of the horror film genre's most improbable monsters. In the past, there have been films about evil cars (The Car, Christine) and evil 18-wheelers (Maximum Overdrive), killer St. Bernards (Cujo) and killer bunny rabbits (Night of the Lepus).
There have even movies about trees that eat babies (The Guardian) and aliens that walk around disguised as plants (The Day of the Triffids). But there has never been a movie about a vine that eats human flesh and talks - or rather mimics human voices - in order to lead prey to its doom.
Even when he was writing the book, Smith says he had doubts about the viability of his killer vine. "I'm usually very private when I'm writing, but at certain points, I shared portions of the book with people close to me, and their reactions made it clear the vine was a dubious choice," he says. "But I felt strongly that if you take the situation and treat it realistically, you can get away with things that are, on the surface, ridiculous."
What was difficult to pull off on the page, however, became infinitely more daunting when transplanted to a film set populated by flesh-and-blood actors. Carter Smith, the first-time director who landed the Ruins gig on the strength of his creepy short film Bugcrush, says he always thought of the vine as "the big unknown" in the overall scheme of the movie.
"If the audience is going to buy that this vine moves and can get into your body and all that, the world of the film has to be absolutely realistic," the director says. "We took elements from lots of different real-life plants when designing our vine. It's in every shot of the film after the characters reach the hill, so it has to look like it could really be growing there. But it also has to look menacing once you realize what it's capable of doing."
Part of what made The Ruins such an intense read is that the desperation of the characters never let up: Smith even went without traditional chapter breaks, so the book unfurled in one relentless rush. In order to give the film the same sense of urgency, the screenwriter made a critical change to the story's first act. In the book, the vacationers are barred from leaving the vine-covered hill by armed guards from a nearby village who threaten to kill them if they try to escape.
In the movie, though, the villagers do more than just threaten.
"Carter and the studio wanted to shut that door right from the beginning with something stronger than verbal threats and shots fired into the air," the writer says. "They wanted you to feel the gravity of the situation of the characters in a palpable way. But that one change resulted in a lot of changes later in the story. In a weird way, the process of adapting the book echoed the plot, in that you make choices that have ramifications you don't foresee."
Smith, who didn't have much involvement with the production after turning in his script, says he hasn't seen the final cut of The Ruins, which underwent major revisions after test audiences laughed unexpectedly at some of the vine's antics, confirming the filmmakers' fears.
The movie also sports a drastically different ending than the book - one of three that were shot during production. "We shot a bunch of different stuff to see what would work best with the finished film. There's a testing process you go through with a studio movie and as frustrating as it can be, it also really gives you a good sense of how an audience feels about an ending.
"Our final decision was informed by what audiences found the most satisfying after watching a really punishing film. I love the ending of the book, but if the movie had ended the same way, the audience would have wanted to kill themselves."
Despite some early positive buzz on the Internet, Paramount Pictures, the distributor of The Ruins, has opted not to screen the film in advance for critics, which is normally a sign that good reviews are not in the cards. But director Smith isn't losing much sleep about what critics think of his directorial debut.
"My initial reaction when they told me they weren't going to screen it was 'Oh, does that mean you don't like it?'" he says. "But genre movies are, for the most part, never screened for critics. I made this movie for audiences, not critics. A theater filled with 17 and 18 year-old kids screaming and jumping will be much more rewarding to me than the idea of some critic writing about the movie."