The others

Grace Stewart is a Catholic mother who lives with her two small children in a remote country house. The children, Anne and Nicholas, have an uncommon disease characterized by photosensitivy, so their lives are structured around a series of complex rules designed to protect them from inadvertent exposure to sunlight.

The new arrival of three servants at the house—an aging nanny and servant named Mrs. Bertha Mills, an elderly gardener named Mr. Edmund Tuttle, and a young mute girl named Lydia coincides with a number of odd events, and Grace begins to fear that they are not alone. Anne draws pictures of four people: a man, a woman, a boy called Victor, and a scary old woman, all of whom she says she has seen in the house. A piano is heard from inside a locked room when no one is inside. Grace finds and examines a "book of the dead," which shows mouring portraits. Every time Grace enters and exits the room, the door closes.
Out in the forest, Grace loses herself in the heavy fog, but she miraculously discovers her husband Charles, who she thought had been killed in the war, and brings him back to the house. Charles says he must leave for the front and disappears again.
Anne and Nicholas discover the old woman is acting as a medium in a seance with Victor's parents. It is then that they learn the awful truth: the old woman is not the one who is a ghost; the ghosts are Anne, Nicholas, and their mother, who is believed to have smothered them in a fit of psychosis, before ending her own life. Grace loses her temper and supernaturally attacks the visitors. This sequence is quickly intercut with scenes from both Grace's viewpoint and the family's.