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. In the fictional universe of
Doctor Who and 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 supernatural threats, occasionally reuniting with the Doctor in the course of her own adventures, all the while continuing to work as a freelance investigative journalist.