The Grudge describes a curse that is born when someone dies in the grip of extreme rage or sorrow, created where the person died. Those who encounter the curse die, and the curse is reborn repeatedly, passing from victim to victim in an endless, growing chain of horror. The following events are explained in their actual order, however, the film is presented in a nonlinear narrative.
In 2001, Kayako Saeki, a housewife living in suburban Tokyo, is in love with college professor Peter Kirk, obsessively writing about him in a diary. Her husband Takeo becomes jealous as he discovers the diary and believes that Kayako is having an affair with another man. Takeo brutally murders her, their young son Toshio, and the pet cat Mar in a fit of rage. After Takeo hides the bodies in the house, Kayako's ghost hangs him.
After receiving a letter from Kayako, Peter visits the Saeki house only to find both her and Takeo's corpses along with Toshio's ghost. Shocked, he flees the scene and commits suicide the next day. The remainder of the Saeki family rise again as ghosts due to the curse, notably Kayako, who appears as an onryō.
In 2004, the Williams family from America move into the Saeki house. While Matt is thrilled with the house, his wife Jennifer and dementia-ridden mother Emma feel uncomfortable. Matt and Jennifer are quickly consumed by the curse. Yoko, a care worker, arrives at the house to find Emma alone before she encounters Kayako, who drags her up into the attic.
Concerned about Yoko's disappearance, her employer Alex sends another care worker, Karen Davis, to take over the care of Emma. At the house, Karen discovers Toshio sealed up in a wardrobe and later on witnesses Kayako's spirit descending from the ceilings to claim Emma.
Alex arrives at the house shortly after and finds Emma dead and Karen in a state of shock. Alex calls the police, with the presence of Detective Nakagawa. In the attic, Nakagawa and his partner Igarashi find Matt and Jennifer's bodies, along with a human's lower jaw. Meanwhile, Matt's sister, Susan, is pursued by Kayako around her office building. At home, Kayako attacks her and she vanishes. While leaving work, Alex is killed by Yoko's jawless corpse.
Kayako begins haunting Karen, who informs her boyfriend Doug of the situation. Karen researches the house, eventually confronting Nakagawa, who explains that three of his colleagues investigating the Saeki deaths were all consumed by the curse. That night, Nakagawa carries gasoline
