Natalie Portman takes audiences on a trip to the unknown in sci-fi thriller 'Annihilation'

Oscar winner Natalie Portman leads the way in the mysterious new sci-fi horror thriller, "Annihilation."

The film is based on the first book of the popular "Southern Reach Trilogy." It takes viewers on a mission into very unfamiliar territory -- a place called "Area X." This mysterious phenomenon appeared suddenly on the U.S. coastline and then started expanding.

Portman plays a professor who once served in the Army, so she knows her way around a gun.

"I had a security guy, actually, who is Israeli during the film, and so he gave me some sort of, like, extra, extra training after hours," Portman said. "We had, of course, arms trainers on set and a stunt coordinator, but I was lucky to have his sort of expertise as well."

Jennifer Jason Leigh plays the psychologist who forms the expedition groups that dare to go looking for answers. "There comes a point where she can't not go in herself and not find out what it is and not find out where she's been sending these people that aren't coming back," said Leigh.

Gina Rodriguez and Tessa Thompson are also part of this dangerous assignment. They said making this movie on location in England was no walk in the park.

"Rainy, cold water up to our waist at times, swampy areas, wet socks," said Rodriguez. "She (Thompson) has a very serious and incredible stunt she did where she's completely in water so she's wet from head-to-toe. We jump in and save her. We're head-to-toe. You know, like, we were in it."

"Annihilation" is rated R and is in theaters Feb. 23.