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.

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?

A news report on a couple looking for their missing son, Ashley, brings a surprise for Sarah Jane (Elisabeth Sladen) when she discovers that the missing boy looks exactly like Luke (Tommy Knight). And when Mr Smith (Alexander Armstrong) confirms that Luke is a genetic match with Ashley, Sarah Jane sends him back to live with his 'parents'. With no knowledge of his former life, Luke finds it hard to fit in and, when he tries to escape, he makes a startling discovery about who his parents really are. Sarah Jane, meanwhile, makes some investigations into the Pharos Para-Science Institute – a research unit that has been conducting experiments using alien technology. Floella Benjamin guest stars as Professor Rivers.

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?

Maria's dad Alan (Joseph Millson) has been turned to stone. The alien talisman is now in the possession of the Gorgon and her evil nuns, and they are preparing to open the portal to their world. Can Sarah Jane (Elisabeth Sladen) and her young friends free Alan from his stony state, prevent the nuns from unleashing more deadly aliens on the Earth, and avoid the Gorgon's petrifying gaze?

Sarah Jane (Elisabeth Sladen) and her young friends investigate reports of a ghostly nun which is haunting the local old folks' residential home. And when one of the elderly residents entrusts Luke (Tommy Knight) with a mysterious alien talisman, it becomes clear there is even more to the story than meets the eye. The gang delves deeper, and discovers that the nun is part of a secret order sworn to protect a terrifying alien creature who can turn her victims to stone with a single look.

A Carcaroth has arrived on Earth, seeking soldiers to help fight his endless intergalactic war back home. Using Combat 3000 to sift out the best, most aggressive and instinctive fighters, he then transports them to his spaceship – awaiting transfer to the war. Clyde (David Anthony) and Luke (Tommy Knight) find themselves amongst the 'warriors', while Sarah Jane (Elisabeth Sladen) and Maria (Yasmine Paige) must infiltrate the alien's headquarters to bring down the Carcaroth from the inside.

The kids escape from the Slitheen and meet up with Sarah Jane at her house. They discover that vinegar will kill the Slitheen so, armed with vinegar bottles, they return to the school and destroy the three adult Slitheen and their machine. Carl, who took on the form of the class brain-box, escapes via a teleport but Sarah Jane assumes that he is dead. Back home she accepts Clyde into the group but asks for him not to tell others about their experiences.

Sarah Jane (Elisabeth Sladen) and Maria (Yasmine Paige) investigate the mysterious disappearance of local boy Lance Metcalf, and soon discover that a number of children have gone missing across the country. Remarkably, the disappearances all occurred during freak storms and in cities that are home to a laser tag game called Combat 3000. As Sarah Jane and Maria delve deeper into the mystery, Luke (Tommy Knight) and Clyde (David Anthony) are off enjoying a game of Combat 30…

Maria and Luke start their new school where they pal up with another boy, Clyde. However, two of the teachers and the class genius turn out to be Slitheens in human form. They are shapeless smelly invaders from another planet whose aim is to destroy the Earth by turning off the Sun with the aid of a machine which Luke inadvertently helps them to start. The three teenagers are chased around the school by the Slitheen family.