Jo Grant was the version of Jo who lived on the alternate Earth ruled by the Silurians.
In 1993, Brigadier Lethbridge-Stewart sent her to retrieve the launch codes for the last surviving nuclear submarine. However, she succumbed to radiation exposure and race memory malaise and turned feral. She was helped by the Seventh Doctor, then both were found and returned to the Brigadier. Jo fell into a coma, and the Brigadier sent a party to London for medical supplies. Impatient, he tried to wake her with drugs to get information about the codes, but killed her instead. (PROSE: Blood Heat)