Liz Shaw first appears in the first serial of the seventh season (1970), Spearhead from Space, having been drafted from the University of Cambridge by Brigadier Lethbridge-Stewart as a scientific adviser to UNIT. She is an accomplished scientist, an expert on meteorites with degrees in medicine, physicsand a dozen other subjects. Her extensive training, however, is still pale in comparison to the Doctor’s own knowledge of the universe and scientific principles far beyond those of Earth. Skeptical at first of UNIT’s ambit to defend against alien invasion, Shaw changes her mind when she encounters the newly regenerated Doctor and becomes involved in defeating the plans of the Nestene Consciousness and its animated plastic Autons.
Liz continues to work with the Doctor and UNIT through encounters with the Silurians, the so-called Ambassadors of Death and the Inferno project, where the Doctor also encountered Section Leader Elizabeth Shaw, an alternative version of the scientist in a parallel universe. She eventually resigns from UNIT and returns to Cambridge; there was no “farewell scene” on screen for Liz, with her departure simply being announced by the Brigadier at the beginning of Terror of the Autons. She reportedly told the Brigadier that all the Doctor really needed was someone to pass him his test tubes and tell him how brilliant he was.
Liz’s life after leaving UNIT is not explored in the series, though in the 2010 The Sarah Jane Adventures story Death of the Doctor one of the UNIT characters mentions that “Miss Shaw can’t get back from Moonbase until Sunday.” Caroline John appeared as an illusory image of Liz in the 20th Anniversary television movie The Five Doctors (1983), and as Liz herself in the 1993 charity special Dimensions in Time.