“The Host” stars Max Irons, left; Jake Abel, center; and Saoirse Ronan, right.
“The Host” stars Max Irons, left; Jake Abel, center; and Saoirse Ronan, right.

The movie poster for “The Host,” opening Friday, features your typical teen-love-triangle image: Saoirse Ronan is front and center with a thousand-yard stare, while co-stars Jake Abel and Max Irons gaze at her longingly from opposite sides. It’s not a surprising setup, considering the screenplay is based on a novel by Stephenie Meyer, author of the “Twilight” saga.

Even the actors know what you’re thinking right now.

“The one thing we’re trying to tell people,” Abel says, “is that [the movie] is more than just that poster.”

And Ronan’s character is no Bella. Possessed by an alien parasite, she’s got the body and internal voice of Melanie while simultaneously existing as Wanda, the alien who’s taken up residence in Melanie’s body. Irons plays Jared, Melanie’s boyfriend; Abel plays Ian, who finds himself drawn to Wanda.

After Melanie/Wanda makes her way to Melanie’s uncle’s desert stronghold, Ian is the first to discover her, nearly dead from thirst. It’s not exactly love at first sight.

“My first instinct is to kill her,” Abel says. “That’s the procedure [to follow in cases of alien possession]. So to get over that was something very interesting to explore: When and how does this enemy start to get under his skin?”

For Jared, the problems start after Melanie/Wanda is brought to the cave in the desert, where he greets the alien-in-his-ex’s-body with a solid slap. “Which is a terrible thing to do, but how would you feel in that situation?” Irons says. “She’s the constant reminder of what you’ve lost in your life.”

Both actors, while grateful for the marketing power that comes with the “Twilight” connection, hope to keep a safe distance and avoid any Team Jared/Team Ian shenanigans. Fortunately, the characters in “The Host” are much deeper and more shaded than those in That Pale, Glittery Vampire Series in the Room; the acting is better, too. What really sets “The Host” apart are the layers of conflict. Even the global battle between humans and invaders isn’t black and white, as the aliens, who just need bodies to live, are a super-polite, peaceful race who turn Earth into a utopia — assuming you don’t have a problem with the whole “bodily possession” element. Eventually, Ian and Jared turn on each other as they struggle with their feelings for Melanie and Wanda.

“I have my view, which is pretty unchangeable,” Irons says to Abel, “and then you have your view, which is pretty unchangeable, and they’re both right. It’s wonderful to have problems like that to play with.”