Maria Bello (A HISTORY OF VIOLENCE, ASSAULT ON PRECINCT 13 (remake)) portrays Adele, an America mother who takes her ten-year-old daughter Sarah to visit her father (Sean Bean of FLIGHT PLAN, LORD OF THE RINGS, SILENT HILL) who lives in an old house on a secluded island. Fifty years earlier there was a cult of people who killed themselves by jumping off one of the cliffs-and the leader of the cult used to live in that same house.
When the daughter disappears they think she drowned but Adele feels that something else is going on. At one point she thinks she's found her daughter, but it is a girl named Ebrill. It turns out that Ebrill has returned from the land of the dead and Sarah has taken her place. We learn how crazy the cult leader was and how he drilled holes in Ebrill's skull.
Adele believes that the only way to get her daughter back is to go to the land of the dead and rescue her. From that point on it's sort of like one of the early NIGHTMARE ON ELM STREET movies, without Freddy Krueger.
THE DARK is just an "okay" horror movie. It seems too heavily influenced by THE RING (remake), as far as dealing with a ghostly little girl, and the movie seems about a half-hour too long. It's based on a novel titled SHEEP, so I suppose anything is a better title.