Sarah Jane Smith is a fictional character played by Elisabeth Sladen in the long-running BBC Television science fiction series Doctor Who and two of its spin-offs. Sarah Jane is a dogged investigative journalist who first encounters alien time traveller The Doctor while trying to break a story on a top secret research facility, and subsequently becomes his travelling companion on a series of adventures spanning the breadth of space and time. After travelling with The Doctor in four seasons of the show they suddenly part ways, and after this she continues to investigate strange goings-on back on Earth. Over time, Sarah Jane establishes herself as a committed defender of Earth from alien invasions and other threats, occasionally reuniting with The Doctor in the course of her own adventures, all the while continuing to work as a freelance investigative journalist.