Sarah Jane Smith is a fictional character played by Elisabeth Sladen in the long-running BBC television series Doctor Who and two of its televised spin-offs. Sarah Jane is a dogged investigative journalist who first encounters the Doctor, an alien time traveller, while trying to break a story on a top secret research facility; she subsequently becomes his travelling companion on a series of adventures throughout space and time. They eventually part ways, but Sarah Jane continues to investigate sinister developments on Earth. She establishes herself as a committed defender of the planet from alien invasions and other threats, occasionally reuniting with the Doctor in the course of her own adventures, while continuing to work as a freelance investigative journalist.