House of 9

House of 9 is a 2004 psychological horror film directed by Steven R. Monroe and starring Dennis Hopper and Kelly Brook. It follows nine strangers who have been abducted and locked inside a house. A mysterious voice called The Watcher tells them that they are to play a game: the last person alive can leave the house and win five million dollars. The film is presented with "live feeds" from hidden surveillance cameras, showing the nine people turning from cooperative escape attempts to a killing fest.

Synopsis from Wikipedia, CC BY-SA 4.0. Everything below written here.

Poster © the film's rights holders.