Whatever Happened to Sarah Jane? (1) (S01E07)

Sarah Jane (Elisabeth Sladen) inexplicably vanishes just as a massive meteor is on a collision course with Earth. When Maria (Yasmine Paige) wakes up one day, she finds that Sarah Jane – along with Luke (Tommy Knight) – seems to have never existed. Instead, a woman named Andrea (Jane Asher) now lives in Sarah Jane's home. The attic is empty, Mr. Smith (Alexander Armstrong) is missing, and Maria is the only one with memories of Sarah Jane. With the Trickster lurking around Bannerman Road and the alien Graske interfering with time, Maria embarks on a quest to uncover Sarah Jane's fate. As she travels back to 1964, will she locate Sarah Jane in time to prevent the meteor from annihilating the planet?