Petra Williams (Inferno Earth)

A parallel version of Petra Williams known in the Inferno Earth as Dr. Petra Williams was the second in command of the Inferno Project at the the Eastchester Scientific Labour Camp. She was loyal to her employers until the true danger was revealed after which she assisted the Third Doctor to get back to his own world.

She was last seen hugging Greg Sutton as the lava from the shaft poured onto the Earth's surface. (TV: Inferno)