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.

Maria (Yasmine Paige) and her dad, Alan (Joseph Millson), dig deeper into the mystery of Luke's (Tommy Knight) new parents and discover that Luke has actually been kidnapped by the Slitheen. There are more shocks when Sarah Jane (Elisabeth Sladen) and Maria find out that Mr Smith (Alexander Armstrong), Sarah Jane's super computer, is one of the bad guys. With Clyde (David Anthony) nowhere to be seen, Luke in the clutches of aliens and no Mr Smith to help, things are not looking good for Sarah Jane and Maria. But just what do the Slitheen want with Luke? And who, or what, exactly, is the Xylok?

Luke and Sky must help the Skullions, but Sarah Jane is in danger too, so who will they save?