Maria and Luke start their new school, but find all is not as it seems. Aided by Sarah Jane and their new friend Clyde, they find the Slitheen, who are enemies of The Doctor, disguised as teachers who have taken control of the technology block and are trying to switch off the Sun. Luke unknowingly gives the Slitheen the code to start the machine, and they start to absorb the power of the Sun. Sarah Jane investigates the company controlling the science block, and Maria, Luke and Clyde investigate the school. Sarah Jane is attacked by a female Slitheen who disguised herself as a company secretary, Janine. Luke finds a secret room and is confronted by the Slitheen commander, his headmaster Blakeman, whilst Maria is hiding under a computer desk after being spotted by Jeffrey. Jeffrey unzips in front of Maria, but the only thing visible to her are his green feet. Maria runs away, and meets up with Clyde who runs away too. They are rescued by the School genius Carl who then unzips to reveal he is a child Slitheen.