Dennis Weaver and Valerie Harper are a couple with three kids.
They are in a car accident, and all of them get out safely, except for one of their daughters. She was trapped in the car after her brother and sister tied her shoe laces together, and the car exploded.
Some time later, the dead girl's ghost comes to terrorize the family, killing her grandmother (Ruth Gordon) by scaring her into a heart attack, pushing her little brother off the roof, and electrocuting her father by pushing a radio into the bathtub. I think the ghost somehow getst her sister to attack the mother with a pizza cutter. The mother survives the attack, and, thinking it was the still-alive sister who had done all the misdeeds, has her committed.
At the end of the film, the mother is in bed and looks up to see the ghost of her dead daughter at the foot of her bed, smiling an evil smile, and screams.