S1·E2 Revenge of the Slitheen (2)

The kids escape from the Slitheen and meet up with Sarah Jane at her house. They discover that vinegar will kill the Slitheen so, armed with vinegar bottles, they return to the school and destroy the three adult Slitheen and their machine. Carl, who took on the form of the class brain-box, escapes via a teleport but Sarah Jane assumes that he is dead. Back home she accepts Clyde into the group but asks for him not to tell others about their experiences.