Rose was just a baby in 1987 when her father was killed by a car. So the Time Lord takes her back to the year in question to the spot where the accident happened. Of course, Rose cannot stand idly by and just watch her dad die alone, so she pushes him out of the way of the on-coming car. But in doing so, she upsets the balance of time and changes history. Suddenly, Earth is under threat from the Reapers, terrifying pterodactyl-like demons that swoop out of the sky to rectify time anomalies.