S01E01: 'Revenge of the Slitheen' Part One

Sarah Jane drops off her young neighbour and adopted son Luke at school, but an unsuspecting science teacher enters the school and is taken over by the Slitheen, with the Headmaster one of their number. During assembly, the Headmaster breaks wind many times and tells form 10B they will visit the new technology block. Luke and classmate Clyde notice that the farts smell metallic, while they later find the canteen food to be rotting and inedible.

Luke is nervous after his first day, but Sarah Jane assures him things will be fine and they will learn together. She ventures online and discovers that new technology blocks have been cropping up in various schools, built by Coldfire construction, but with a mysterious space unaccounted for in each of them. The Slitheen Headmaster and science teacher disable the region's power supply from their control room, but soon have to restore it when the system overloads.

Maria's dad tells Sarah Jane that his ex wife ran off with the judo instructor and reveals he was involved in building the technology blocks. Sarah Jane decides to investigate the mysterious space in the one in her local school.

In science class Luke unveils a great knowledge of science, with the teacher inviting him and portly pupil Carl to a lunchtime session. Luke unwittingly gives the disguised Slitheen crucial advice on how to improve the damaged transformer to stabilise the power. Later, the teacher and Headmaster are elated with this new breakthrough and declare they will end the planet that night.

In the school, Sarah Jane discovers that everything is rotting sooner than it should, but she is being observed on CCTV by a Slitheen called Janine from Coldfire. They later meet and Sarah Jane confronts her with her findings, but after she ignores her threats to leave, Janine unzips herself and her true Slitheen form becomes apparent.

Maria, Luke and Clyde head off to investigate the new block after school. Maria is found by the science teacher in a classroom. He is angered by her and sheds his skin, and gives pursuit to the fleeing Maria, while Janine is hunting down Sarah Jane via her perfume.

Luke is soon trapped with the Headmaster and Maria and Clyde are joined by Carl to take refuge, but the swot sheds his skin and proclaims that he is a child Slitheen looking forward to a hunt.