Rose (Radha Mitchell) and her husband Christopher da Silva (Sean Bean) are concerned about their adopted daughter Sharon (Jodelle Ferland) who has been experiencing several nightmares and has begun sleepwalking. Their only clue to the girl's condition is her repetition of the name "Silent Hill." Desperate for answers, Rose takes Sharon to the town of Silent Hill, West Virginia, despite Christopher's opposition. She reaches the town, chased by a suspicious female police officer on a motorbike, but is knocked unconscious in a car crash, and awakens to find Sharon missing.

Rose searches the empty streets of the town for her missing child. Instead, she encounters a series of monstrous creatures and a ragged woman named Dahlia Gillespie (Deborah Kara Unger) who speaks of the terrible things done to her own daughter, Alessa, by the townspeople. Dahlia claims that Sharon is actually her own daughter, not Rose's. After she exits the scene, Rose eventually encounters the police officer who chased her, Cybil Bennett (Laurie Holden), who immediately arrests her.

Upon discovering that the road out of the town has mysteriously disappeared, they are attacked by a deformed creature, and Rose escapes handcuffed. As events unfold, Cybil allows her to go free and the two work side-by-side to survive in the hellish town.

Scenes of their search are interspersed with scenes of Christopher's search of the town, with the reluctant assistance of Officer Thomas Gucci (Kim Coates), who grew up in Silent Hill. Christopher discovers documents showing the town was abandoned after a terrible fire 30 years ago, along with a photo of Dahlia's daughter, who bears a remarkable resemblance to Sharon. Christopher is arrested by Officer Gucci when he tries to question the orphanage about Sharon and Alessa, and is told to stop investigating Silent Hill.

Meanwhile, Rose and Cybil find refuge from Silent Hill's monsters in the town church, where they discover the remaining townspeople, a religious cult, headed by Christabella (Alice Krige). After convincing Christabella that she wants to find "The demon" so feared by the
townspeople, Rose is taken to a hospital in the town, along with Cybil. Here, Christabella discovers the likeness between Sharon and Alessa - via the photo of Sharon in Rose's locket - and condemns Rose and Cybil as witches. Cybil is captured and beaten with pipes by the townspeople while Rose escapes the clutches of the cult and descends into the basement of the hospital. Rose eventually encounters a badly burned figure - Alessa - in a hospital bed and a mysterious little girl who strongly resembles the missing Sharon. In an extended flashback, Rose discovers that Silent Hill has had a history of ritual witch burnings, and that an attempt to burn Alessa 30 years ago went disastrously awry, resulting in the
devastating fire destroying the town. Rose is told that Sharon is a manifestation of Alessa's remaining innocence and goodness, and was taken to the orphanage and subsequently adopted by Rose and Christopher. Rose asks the little girl who she is and is told "I have many names. Right now, I'm the dark part of Alessa." Rose agrees to help Alessa gain her final revenge.

Rose enters the church soon after Cybil is burned to death by the townspeople, and Sharon is about to suffer a similar fate. She confronts the townspeople and Christabella with what she knows, attempting to convince the cult that they are in denial of their own fate. Angered at what she believes to be heresy, Christabella stabs Rose. Rose's blood drips onto the church floor, opening the way for Alessa. The adult Alessa and her doppelganger rise out of the pit, and proceed to kill Christabella and the townspeople with huge tangles of barbed wire, leaving Dahlia the sole inhabitant of Silent Hill. As the carnage ensues, Rose rescues Sharon from the fire and protects her. Sharon looks up to see Alessa's dark double looking down on her. Before Rose and Sharon/Alessa leave, Dahlia asks why Alessa did not kill her, too. Rose replies with the words that Cybil had told her in the hospital: "Mother is God in the eyes of a child." Rose and Alessa leave Silent Hill and return home. Nevertheless,
although Rose and Alessa are in the same room as Christopher, they cannot see each other - the world inhabited by Rose and Alessa is shrouded in mist.

The 'real' Silent Hill
In researching the different elements of Silent Hill, screen writer Roger Avary was inspired when he heard of Centralia, Pennsylvania, and decided to base the film on it. The population of the town has dwindled from over 1,000 residents in 1981 to 12 in 2005 and 9 in 2007, as a
result of a 46-year-old mine fire burning beneath the borough.

In 1962, an exposed vein of coal ignited, due to the standard policy of burning the garbage on a weekly basis in the borough landfill. Attempts to extinguish the fire were unsuccessful, and it continued to burn throughout the 1960s and 1970s. Adverse health effects were reported by several people due to the carbon monoxide produced.

In 1984, Congress allocated more than $42 million for relocation efforts. Most of the residents accepted buyout offers and moved. Today a handful of occupied homes remain in Centralia. Most of the buildings have been razed, and at casual glance the area now appears to be a meadow with several paved streets through it, and some areas are being filled with new-growth forest.