Hardin was an Earth scientist.
Hardin was brought to Argolis by Mena to get the Tachyon Recreation Generator working properly so it could rejuvenate the Argolins. His assistant, Stimson, had convinced him to fake success in their experiments to ensure continued funding. With the aid of the Fourth Doctor and Romana, he succeeded in rejuvenating Mena and Pangol. (DW: The Leisure Hive)