Thirty years ago, in the Carpathians Mountains of Romania, a group of explorers blows an entrance to a cave hidden under a church, but the explosion causes a landslide and they become trapped inside.

In the present days, the expedition leaded by Dr. Nicolai and his assistant, Dr. Kathryn are exploring the place and they find the access through an underwater river, requesting the experienced cave divers team leaded by Jack. Dr. Nicolai discovers that, in accordance with the local legend, the church was built to seal the cave as a display of God's protective power, and that Templar Knights entered the cave to fight winged demons.

When the group reaches a cave though a tunnel one mile below and three miles in, a creature attacks one of the members and his breathing apparatus explodes, collapsing the tunnel and trapping the group in the cave. Sooner they realize that they are the rescue team and they have to find an exit to survive from the attack of the monsters.

× Filming Locations:
• Leighton Hall, Carnforth, Lancashire, England, UK
Lincoln, Lincolnshire, England, UK
Pickering Station, Pickering, North Yorkshire, England, UK (view)

• Also known as Prime Evil.

• Different DVD Versions: German version of the DVD include interviews with Lena and the cast, check the different country versions.

• Lena Headey starred in the movie Imagine Me & You (2005) together with Piper Perabo as well.

• Lena Headey also starred in the short film The Sophisticates (2008) together with Piper Perabo.

• Filmed mainly in Romania, a country with over 12,000 registered caves.

• The film claims to have some basis in truth because new micro-ecologies have been discovered in deep caves, especially in Romania. According to film consultant Dr. Christi Lascu (acclaimed speleologist and Romanian editor of National Geographic magazine), 35 brand new species were found in the Movila Caves in the late-1980s. Among the species found was a 10cm centipede with a poisonous bite. There was nothing the size of the creature in the movie, but in theory there is not a limit for the size of animals living down there.

• The actors sometimes had to spend up to 10 - 12 hours a day in a wetsuit, constantly in and out of the water.

• A 750,000 gallon tank was created to shoot underwater photography.

• Bruce Hunt's direction debut.

• One of the scenes at the beginning of the movie uses the same set as Underworld: Evolution (2006).

× Awards: None Recieved • "That was crazy! It was three months in the water in Romania. After the first three days, I didn't even want to put the wet suit on again. Bucharest is hell."

• "I never considered I'd be running around from a monster. And I read it and I thought 'Why not' because this is my job and why not try all kinds of genres. And I did it, and possibly will never do it again."

• If she got any injuries during the filming
"No. No injuries. It was just hysterical. It's good to kind of try everything. And, you know, to be chased by a guy in tights wearing a monster head is something I'd never imagined I would be doing in Eastern Europe. And that was just a man I had met... in Bucharest."

• On filming the movie
"That was tough. That was being wet for about three months in Romania, which is not a great combination; and being chased by a man in tights with a big monster head. What can I say? You have to try everything I think." • Kathryn: At first, I thought it couldn't survive outside of a cave environment. Now, I'm not sure. I think it wants to get out. • Coming Soon!