Grace Stewart (Nicole Kidman) is a devout Roman Catholic mother who lives with her two young children in a remote country house in the British Crown Dependency of Jersey in the immediate aftermath of World War II. The children, Anne (Alakina Mann) and Nicholas (James Bentley), have an uncommon disease, characterized by photosensitivity, so their lives are structured around a series of complex rules to protect them from inadvertent exposure to sunlight. The arrival of three servants at the house â aging Mrs. Bertha Mills (Fionnula Flanagan), elderly gardener Edmund Tuttle (Eric Sykes), and a mute girl named Lydia (Elaine Cassidy) â coincides with a number of odd events, and Grace begins to fear there are unknown others in the house.Anne draws pictures of four people she has seen in the house numerous times: a man, woman, a boy called Victor, and an old woman. Grace finds a 19th-century "book of the dead", an album of mourning portrait photos of deceased family members from a previous generation, with some missing pages. She hears noises in the house. With the servants, she tries hunting down the intruders but cannot find them. She does not believe her daughter has seen the others until she hears the ghosts herself. Convinced that something unholy is in the house, she runs out in the fog in search of the local priest to bless the house. Meanwhile, Mr. Tuttle is covering gravestones under autumn leaves.Outside, Grace discovers her husband Charles (Christopher Eccleston), whom she thought had been killed in the war, and brings him back to the house. Charles is distant during the short time he spends there, and Mrs. Mills says, "I do not think he knows where he is." During this time, Grace attacks someone dressed up like her daughter; she is frightened by the face she sees underneath Anne's First Communion veil. However, she finds that she has actually attacked her daughter. Mrs. Mills tells a distraught Anne that she too has seen the unknown people in the house and that big changes are coming. Charles says he must leave for the front and Grace wakes to find him gone again.One morning, Grace hears the children's screams: all of the curtains in the house have disappeared or have been taken down by the intruders, as Anne had said they might. When Grace sees the servants are not alarmed by this, she accuses them of being involved and banishes them from the house. That night, Anne and Nicholas sneak outside to find their father. Anne discovers the graveyard, which the servants have uncovered, and realizes that these are the servants' graves. At the same time, Grace finds a photograph from the book of the dead and is horrified to see it is of the three servants. The servants appear and follow the children back to the house. Grace has the children hide upstairs, while Mrs. Mills reveals that the three servants died of tuberculosis more than 50 years before. Hearing the children scream, she tells Grace to go upstairs and talk to the intruders.Grace walks upstairs to the bedroom with her rosary beads. There, she discovers that the old woman whom Anne had described is acting as a medium in a sÃ©ance with Victor's parents, talking to Anne. The medium asks the children questions about how they died. The children begin to scream that they are not dead. In a frenzy of denial, Grace shakes the sÃ©ance table, and rips the papers on which the medium has been writing. Victor's family sees only the table shaking and the paper being ripped. In using this supernatural incident as proof that they are not welcome in the house and should leave, Victor's mother reveals that Grace had smothered her children then shot herself.As Grace and the children huddle together in shock in the darkened school room, her memories return to her: stricken with grief for her missing husband, isolated by the children's condition and the servants leaving her, Grace lost her mind and smothered her children with a pillow. Realizing what she had done, she shot herself. When she then "awoke" and heard her children's laughter, she assumed God had granted her family a second chance at life. Anne asks if they are in Limbo; Grace is no longer sure of her Catholic teachings.Mrs. Mills tells Grace that they will learn to get along with the intruders who periodically come to the house, that sometimes they will notice them and sometimes they will not. The children find they are no longer photosensitive (as they are no longer living), and for the first time, they can enjoy playing in the sunlight. Victor's family, unable to rid the house of its former occupants' spirits, drive away as Grace and the children watch. Although the property is again put up for sale, Grace and the children are firm that "this house is ours," and "no one can make us leave."
Output: Question: How did Grace kill her children?, Answer: smothered them