S01E02: 'Revenge of the Slitheen' Part Two

Sarah Jane manages to escape from the Janine Slitheen by spraying her perfume at it after the alien boasts of its powerful sense of smell. Maria, Clyde and Luke are chased by the Slitheen around the school, with Sarah Jane calling the latter to tell him to use something smelly to escape.

Sarah Jane arrives on the scene and opens the door with her sonic lipstick, allowing her friends out, before sealing the Slitheen inside.

Clyde threatens to call the police unless the others tell him more about the aliens and Sarah Jane.

Headmaster says they will have money to buy a fleet of battle cruisers and then return to home planet and make their fellow race beg for mercy.

In her attic, Sarah Jane opens up her computer 'Mr Smith', which shocks Clyde. They discover that Coldfire have put up mysterious buildings across the world, connected by underground tunnels. Luke realises the information he gave his science teacher will help them destroy the world.

The Headmaster contacts the other Slitheen units around the world and tells them to prepare for the implementation of their fiendish plan. Luke hatches a plan to sever the transmitter system by returning to the school, but the Slitheen power drain has already begun in America and is spreading across the globe and to the UK.

Clyde mentions that the science teacher was scared by his cold chip sandwich earlier in the day, with the gang working out that the vinegar must have been the agent that made him fearful. They raid the kitchen before heading back to the school, just as the Sun is switched off.

The Headmaster takes his human skin off and confronts the quartet. But Maria douses him in vinegar and he explodes. Under attack, the father Slitheen and his child summon the rest of the family, via transmat, to the school. They quickly capture the humans, but Luke claims that he miscalculated when he gave the science teacher the vital equation earlier and that the system will explode.

Sarah Jane throws her sonic lipstick to Luke, who legs it and destroys the Slitheen device with it. They flee the exploding control room, but the father Slitheen and his child are trapped by the closing door as they try and escape. They beg Sarah Jane to open the door to release them, with the father pleading with her to let his 12-year-old son live.

Sarah Jane is motionless and the two aliens subsequently explode. She feels sad, but Clyde argues that it was "them or us". Later, Sarah Jane opens up to Clyde and explains that she started off in her unique life by asking questions, before letting him in on her relationship with The Doctor.