Basically, the house is haunted by the spirits of the 3 people, the kid, wife and husband. The husband flipped out because he thought the wife cheated on him and that the kid was not his, so chop/slice, wife sashimi. Then he gets wacked by a car outside in his rage, his spirit sticks around. Asian beliefs about ghosts and such is that if you die with strong emotion about something, like grief or rage, or if you left something really important unfinished it consumes you and it doesn't let you go to the ghost world until the curse is broken or the deed is accomplished. You can see the thing kinda playing out again with the new owners. The wife (I think Hirumi) gets scared shitless and goes comatose, then the husband finds her and freaks, see the ghost kid, gets sorta possesed/influenced by the spirit of the murdering ghost husband. The interesting part is that Rika the volunteer actually lets the curse continue. Remember when she untapped the closet door and let out the cat/kid? The young husband was the one that originally taped it shut. His and hirumi's chapter happens first chronologically. So eventually everyone who is connected with the house in some way falls victim to it's malice. The only way to break the curse according to my taiwanese friend the ghost movie expert is usually to help the ghost in some way, or in this case burn the house down. The retired cop almost got it done. Rika almost did too, but the husband got her at the end. The ghost wife, Kayako, does most of the killing, but actaully wants help, she is afraid of the husbands spirit still. That's why at the end you see the wife as she actually was, with the whole hand over the face thing. Unfortunately for Rika, she stayed too long and the husband ghost got her. The husband's rage and the wife's grief is the driving force of the curse, hence the name of the movie.