Sarah Jane (Elisabeth Sladen) mysteriously disappears – just as a huge meteor threatens to crash straight into Earth. When Maria (Yasmine Paige) wakes up one morning, it's as though Sarah Jane – and Luke (Tommy Knight) – never existed. Living across the road in Sarah Jane's house is a woman called Andrea (Jane Asher). And with the attic empty and Mr Smith (Alexander Armstrong) nowhere to be seen, every other trace of Sarah Jane has vanished – and Maria is the only one able to remember her. With the mysterious, hooded figure of the Trickster haunting Bannerman Road and the alien Graske meddling in time, Maria sets out to discover whatever happened to Sarah Jane. But as her journey takes her back to 1964, will she be able to find Sarah Jane in time to stop the meteor from destroying the world?

Maria (Yasmine Paige) finds herself taken back in time by the alien Graske to a pier in 1964. There, she meets a young girl her own age called Sarah Jane Smith (Elisabeth Sladen) who, with her friend Andrea (Jane Asher), is about to embark on a fateful adventure. Taken by the Graske again, Maria is then reunited with the present-day Sarah Jane. But with them both trapped in limbo as part of the meddlesome Trickster's plan to wreak chaos, they are helpless to stop the huge meteor which is about to crash into the Earth. Maria's dad Alan is the only one able to remember Sarah Jane and Maria and faces a struggle to bring them back in time to save the world.