Jacob, an unpopular pupil at school, finds an alien pendant. He begins using it to control other people, while leaving a strange blue handmark on his palm. Rani finds the pendant in the school bathroom and, upon learning its effects, leaves it in Sarah Jane's attic.
Meanwhile, Clyde's father Paul returns to Clyde's house, years after leaving his family for Clyde's aunt in Germany. Clyde takes Paul to the attic to prove he fights aliens. Paul pockets the pendant, and uses it to force Rani's father Haresh to do push ups indefinitely. When Luke and Rani turn up, Paul uses the pendant to make Clyde forget about Luke, Rani, and Clyde's mother Carla, and the two drive off to travel the world. Paul uses the pendant to steal expensive objects to bond with Clyde.
Luke and Rani contact Maria and her father, Alan in Washington, D. C. and they hack into UNIT's database to find a match of a drawing of the pendant Luke and Rani send to them. 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.
