The Mark of the Berserker

Luke is going for a sleepover at Clyde's house whilst Sarah Jane goes away for the weekend. Clyde's estranged father Paul turns up hoping to get to know his son. Jacob, the unpopular kid in school, is in possession of an alien pendant. Jacob discovers that he can use it to control other people, while leaving a strange blue handmark on his palm. When he takes a teacher's and other student's voice in a detention, Jacob rushes to the bathroom to wash the handmark off. When he successfully does so, Rani knocks on the door and distracts him. Jacob leaves the room but hides outside. Rani enters the bathroom cautiously, and finds the pendant. When she discovers, through instructing her father Haresh, that it can control people, she takes it to Sarah Jane's house for Mr Smith to investigate it. Sarah Jane, however, has disabled Mr Smith while she is away. Rani leaves the pendant hanging on a roof beam. Clyde tells Paul about the adventures he has with Luke, "saving the world". When his father does not believe him, Clyde takes him to visit Sarah Jane's attic. While Clyde shows him some of the objects in the attic and tells him about Mr Smith, Paul notices the pendant and pockets it. When they leave the house, Haresh spots them and comes over to investigate. In possession of the alien pendant, Paul discovers that he can control people, after making Haresh a victim of the pendant for the second time that day. After Luke and Rani turn up, Paul instructs Clyde, over whom he now has control, to forget who they are and that he has ever seen them before. Clyde, as he must, accepts his father's command.

After Clyde goes off with Paul, Luke and Rani ponder about what to do to save their friend. After unsuccessfully trying to contact Sarah Jane, who is pursuing a mischievous slug-like alien in a hospital, they contact Maria and her father, Alan, in Washington, DC. They send a picture of the pendant to them to investigate as Alan can hack into UNIT. They discover that the pendant belongs to a race of alien warriors known as the Berserkers, and that using the pendant can change the user into one of them, including marking their hands and turning their veins blue. Haresh refuses to stop the pressups and Paul gets everything he wants for free, and uses this as a bonding method with his son. He instructs Clyde to forget about how he left him and his mother, Carla, when he was young and, indeed, to forget about his mother.

Luke and Rani head over to Clyde's house and explain the situation to Carla. Together, they get into Carla's car and drive off to find Clyde and Paul.

The effects of the pendant take over Paul's skin and his mind. He cannot control it and collapses, but then stands up, now possessed by the pendant. He announces that he is the Berserker and that Clyde is his soldier. Sarah Jane appears and Clyde recognises her. She tells him that Carla, Rani and Luke are the most important people in his life when he asks who they are. Clyde and Carla talk Paul through his memories, whilst Sarah Jane shows him a reflection of himself in the mirror, and he remembers who he really is. Everyone who the Berserker commanded has their commands undone. Clyde tries to get his parents back together, but Paul tells him that he has got Carla's sister pregnant. Clyde tells his father he does not need him and not to mess up with this baby. Clyde tells Carla to forget about the pendant, what she knows about Sarah Jane's adventures with her son, and Paul. Clyde chucks away the pendant, into the sea. Sarah Jane reveals that her parents died when she was young and she would do anything to see them again. When Clyde is gone, she takes out a picture of her mother and father and rubs her finger over the latter.